1. Name the image what is showing in the picture

2. Describe briefly what the picture is or what it means in alt text

3. Make sure to allow your images folder to be crawled in robots.txt. It would be a shame to go through all that work and have the image folder blocked

4. Mark up your images with schema: http://schema.org/ImageObject

While the tagging system is nice, it can be a killer for seo. Tag pages generally have thin content, and a lot of links i.e. bad for Googel guidelines. If you want to help your users, and still use the tagging system, set the tagging pages to "no-index"

As to the categories URL's I would add them. Think of your site like a book, and your categories like the chapters. Setting your site up with categories also allows you to potentially have another focus keyword in your URL, and helps users navigate your site easier

We have been round and round with this as well. Most likely it is from the user having just created an account, and with no other activity left a good review for your business. When we have people leave reviews for clients on Yelp, we always ask that they go out and leave a few for places they like before leaving a review. This helps the account to be seen as more "realistic".

I remember a case where companies began suing people that left reviews.

And I'll just leave this here:
Link

"John may sound paranoid, but he's got company. During interviews with dozens of business owners over a span of several months, six people told this newspaper that Yelp sales representatives promised to move or remove negative reviews if their business would advertise. In another six instances, positive reviews disappeared — or negative ones appeared — after owners declined to advertise."

In my opinion, get people to leave reviews for your business on Google places. Yelp's review system and business practices seem to be driven more towards monetary gain.

*edit BTW, I would not advertise on Yelp. We have tried it many times, using different techniques and it never pays for itself. The truth about Yelp ads is: unless people are seaching on Yelp for your services, they won't find you. It's true that your Yelp profile might come up in organic Google search results, but paying for ads on Yelp wont help that any. Most are going to search on Google, and I would dedicate my focus to improving your position in those results.

I would start here my friend. Since this is a technical question, I would try contacting MOZ directly. From my experiences, they have very good service and response times.

https://moz.com/help/contact

Take a look at the image index rate, and see how many are indexed and showing. 20k images is quite a bit, and I would want to see if Google actually indexed them all before I started creating redirects for that many items.

If they are indexed, see if there is a way on your new site's sytem to have the images named the same. That way you would only be creating a redirect for the image paths, and not the images themselves. Example:

oldsite.com/image/25/coolpicture.jpg
newsite.com/images/awesome/25/coolpicture.jpg

All that would be needed would be an HTACCESS rule redirecting from one directory to the other, using the image name as a variable. You could probably redirect most of them using only a few rules than 20,000 separate redirects.

Is it worth it to redirect? I think that depends on how many are indexed, and if the images bring you a significant amount of traffic.

Anyone can edit a Wiki page = bad for your business. If you can't control it, or constantly have to edit what people type it's not worth the time investment.

Wiki outranking your main site =  bad for your business. Here's why: Wiki often has a ton of references and links on a page about a business. The chances that a user will click one of those and navigate away from your page is very high. Worse case would be that a user clicks a similar business, that is a competitor of yours. Think of it like having the "related videos" displayed at the end of a youtube video. They click, they leave, you are not thought of again. One thing to remember when advertising on the internet; It is your job to convince people to use your services. People that do not know your business don't owe you anything, and have no brand loyalty to your company.

I agree with EGOL. I see what you are trying to do, but I would try and capture that traffic and content for your own site, then to give it away to Wikipedia.

"So, if these guys don't even have their own queries nailed down then they either are not very good at this or the cost isn't worth it even for them."

Sounds legit. This seems to be a bait and switch service directed at those unfamilar with seo to get them intrigued. Gotta love those pesky seo emails selling dreams every day! We get quite a few of them here. Most go straight to the trash folder. Wonder what they tell the client when it doesnt work and they don't show up in auto suggest? lol