This article explains "search visibility" and has a section on how it is calculated...

https://moz.com/blog/mobile-rankings-search-visibility-moz-analytics

Keep in mind that infringers post images on their website without any references to licenses.  They stole the images, why would they point to a license ? !!

Many of the "free image sources" on the web contain a significant number of infringing images.   Furthermore, many of the websites that sell or license images are offering images that they have no right to offer.  I have found my own images on such sites and have done something about it.

On many of the free image websites and some of the websites selling images the images are uploaded by "members".  The owners of these sites simply claim "safe harbor" when infringing images are found on their sites.  They simply blame the member and take the images down when someone complains.

I am not an attorney, but I can say that I would not use your proposed method because a lot of the images that you think are OK are not OK.   Furthermore, the images to which I hold copyright do not have licensing information posted with them because they are not available for license by anyone at any price.  They are for my exclusive use.

People who are serious about protecting their images from infringement will probably do at least two of the following if they see their images on your website.... DMCA to search engines, DMCA to hosting services, complaint to Adsense, complaint to other revenue sources, send informal notice to you, demand payment for your past use, add your website to the list that their legal team will look into.

It might be a good idea to make an appointment with an intellectual property attorney and discuss the concepts of copyrights, permissions, licenses, documentation, fair use, safe harbor and how copyright laws vary outside of your home country.  I have had these types of meetings with more than one attorney and found that it is not as expensive as you might fear.  After that meeting you have a person who knows you and can be a quick source of assistance if needed.  Time and money well spent.

If your freelancers obtained "royalty free" images then they will likely have a receipt proving that they paid a fee for each image that was granted a royalty free license.  If they obtained other forms of license or permission they should have that neatly logged in a spreadsheet or in the form of email messages.  That is where I would start with this.

If you don't have any documentation then it is going to be really hard and really costly to go backwards to determine where each image came from and if proper permissions and licenses were obtained.  That might cost more than doing the work over again.  If I was in this situation, I would start over on this project.

If you are getting into the business of using the images of others then a good education in copyright, fair use, licensing, permissions, and proper documentation is essential.  In addition to you having this information and knowledge, anyone who works for you must have it because the problems of infringement will be yours and not theirs.  Lots of people run wild and rampant when collecting images for their websites or client websites.  They simply don't understand copyright law or the problem with ignorance.

Will people get in touch with you before filing a DMCA or filing a copyright infringement lawsuit?   They might or they might not.  If they think that your website is run by scofflaw organization with few assets then they will probably just file DMCAs with search engines and hosting companies.  They might also file complaints to Adsense and other income sources.  Successful DMCA and Adsense complaints will put the infringer out of business.  I make lots of these complaints against infringers and have a system in place to do them quickly and efficiently.

If your website appears to be run by a substantive company and the person who's images you infringed is a decent and patient, they might send you an informal infringement notice, give you a chance to fix it, and then file DMCA and income source complaints if you don't respond quickly.  Or, they might send you a bill for your past use of the image and a license agreement for use of the image going forward.   If you have stolen a lot of their images or you have a person who stands firmly on their intellectual property, they could go straight to a lawsuit or other legal remedy.

The owner of the images enjoys the ability to chose their methods of dealing with you.

"I guess it would be logical to filter only Non-Branded keywords, right?"

That is a good idea.   I keep mine in a separate campaign at semrush.

I really like visibility metrics because they are a single number that summarizes my competitive standing for a large number of keywords.

Are visibility metrics skewed?  Absolutely.  They are skewed because we select the keywords - the boundaries of comparison.

If we pick a large number of keywords that are representative of the industry area in which we compete, then that might not be extremely skewed.  However, since we define the basket of keywords ourselves, then we skew the metric in proportion to the keywords that we include that are specialties of our business.

I think that you should monitor the branded keywords of your business.  Knowing what's happening there can tip you off to health problems of your own website or people who might be infringing upon your intellectual property.

"Google declared the max number as 100 internal links."

This is old information.

"Avoid Too Many Internal Links" error from Moz "

I think that Moz needs to rethink this, though I know a lot of people will disagree with me... but I am willing to bet big on myself.

OMG!  No!

If you would have earned #1 position from the beginning of Google, that would have been your best opportunity to have organic traffic that matched what you see in Google Trends.   HOWEVER, Google has become, a better webmaster, more concerned about meeting shareholder expectations, and has begun modifying the format of the search results pages to keep you on their search pages for more page views, display more ads, display more ads at the top of the SERPs, increase shopping results income, make more money.   So, if the #1 organic position, would have remained at the tippy-top of the SERPs for all of those years, then your traffic graph might be similar to Google trends.  Instead, the reality is that your traffic graph would have shown either a much steeper decline or much less dramatic growth.

I use live chat boxes frequently when I am shopping.   They often allow me to get an immediate answer from the company.

I don't like the ones that pop-up in my face.  Instead I prefer an obvious link or a logo that I can click to trigger the chat box.  When I use the chat box there is a very high probability that I will make a purchase and a much lower probability that I will return the purchased item.

I do not use live chat boxes on my own websites.  Why?  The same reason we don't have a phone number and our email address is hard to find.... because we are mainly a content shop and almost every question a buyer will have is answered on the website.  Instead of a link to a live chat we have links to an extensive content library.  The goal is to serve thousands of people per day with the content rather than serving them one-on-one with calls, chats, emails.

Lots of people do not like this business model, but it is a legitimate business model.  And, once you have purchased from us you get our phone number email address and we will respond generously to your questions... but those are usually links or guidance to pages on our website that have an article, video or photographs that answer the most common customer questions.

We have a website with a page that links to events in our industry.

Most of the events have a single homepage that is updated every year.  These homepages have a description of the upcoming event and links to agendas, registration, lodging, sponsors, speakers, exhibitors, past year highlights, etc.   If you do this your search engine visibility will develop over time because almost everyone that links to your event will link to this single page year after year, for all of their websites, and every time they mention the event over time.   Also, repeat visitors will be familiar and getting information, registering and finding lodging is "just like they did last year".

However, other events change the URL and everything else every year.   This is a really bad idea because employees at businesses like mine, who link to events, will be snarling when they see that you have changed the URL again and must go on a treasure hunt to find it.  Potential attendees will have trouble finding your event too.   We have stopped linking to some of these events because finding the new pages, updating the links, and editing information is too demanding of employee time.  We have not deleted a lot of events.  Just the ones that are pain in the butt.  When they get in touch with us to complain we tell them, let us know when you are done playing musical URLs.

All of my 301 redirects will still be in place when I attend my own funeral and my business succession plan orders the new owners to maintain them.

If you don't redirect and there are still links out there on other websites, Google spiders will not follow them to your site.  Human visitors who find these links and click them will discover air instead of your website.

Two stories...

One of my competitors has their site redesigned about once a year.  Twice in the past three years their designer tossed the new site up with noindex on every page.      We notice right away but it usually takes them a week or two to figure out what's happened.  When the remove the noindex the site returns to normal in a few days.

I noindexed a folder of 80 thin content pages immediately after Panda 2.0 in April, 2011.  I allowed the pages to be open to visitors because they had some good photos and data tables on them.   The site escaped in the Panda 2.1 about a month later. 

Then, I started publishing same-topic articles on the same URLs, using all of the original content that was noindexed.  When the article is finished, I remove the noindex.  A new articles has the noindex removed about once a month.  (It takes a long time to republish 80 pages at the rate of one a month.)

These URLs reside two clicks from the homepage on a long-established and reasonably powerful site.  When I remove the noindex the amount of time for the page to start ranking can vary from hours to several weeks.  A few times I went into the code to see if I forgot to remove the noindex - and I had not forgotten.   Some of these page go right to the top of google for competitive terms.  Others have trouble getting reindexed even though we point internal links to them on many parts of the site.  We have waited a couple of months for some to be reindexed.

Good luck.