There is no standard answer to your question.  In addition to Mcarle's great answer, you can see what the creator of an image has to select from here...  http://creativecommons.org/choose/

There are plenty of sites doing this successfully, and they don't have any problems.

I agree with Bill's answer.... but I think that this is something that Google or other search engines could change their mind about.

I write a blog that links out to a couple dozen articles on the web every week.  I don't link to anything that is behind a read gate.  Why?  I believe that most of my visitors will be disappointed to hit the readgate.

I think that Google could see searchers click on a listing in the SERPs, hit a read gate, bounce off, and decide that they did not give the searcher a good experience - and thus demote the content behind read gates.  If I was the boss at Google, that is what we would be doing.

Pages with lots of images can be great assets for your website.   I have pages with 40 to 50 to 100 images (nice size images) that rank at the top of Google for really really difficult queries - and in my opinion the images are the reason why these pages rank so well.  People love visual content - especially if it is beautiful, interesting, surprising, funny, etc (long list of other reasons).

"The other part, and I see this happen a lot especially with bigger clients, is when you put lots and lots of images on one page, like an image gallery, those pages tend to be very hard to get indexed. The reason for that is there's not a lot unique textual content. A lot of times it's just overwhelming to users. It doesn't provide a lot of benefit in a search result."

heh... my response to this is... Get off of your butt and write some captions.  If you have created all of those awesome images you must know something about them.  They say an image is worth a thousand words.  Get busy.  If visitors see a great image they want to know.... Who?  Where?  How?  WTF?   Should be really easy for you to write that.

I have some pages where I have spent $1000 to $2000 just to create the images.  Some are graphics, some are photos, some are graphs based upon data.  Images are my best content and my competitive advantage.  I spend thousands of dollars a month to create and acquire some of the best images in my industry.

It sounds like you have a lot of great images and are sitting on a fantastic opportunity.  Write about your images and see what happens.  You might be surprised at what happens.

Use the title for something better, something more descriptive (wow just think of all that extra space!).

Absolutely.   I don't have space in my title tags for the domain.  They are going to see the domain below the title in most search engine SERPs.

Just saying what I believe and what I do.  Not saying that it is "right".

I don't want to call images from another domain.   I want google to see me as the source for all of my content.

I also don't want to rely on the manufacturer's server.  My sites are on fast, dedicated servers on a host that has almost zero downtime... only moments of downtime in the past decade.   Don't bet that delivery will be faster from the manufacturer.  Bet on yourself.

Manufacturers often have idiots running their websites.  They can put HUGE image files out there that download slowly.  Manufacturer's web team might move images around their server and not notify you.  They might also upload new images without telling you.   It can take you a while to realize that the images are missing or switched and in the meantime their idiots are making your website look like crap.  After they change or move images try to sort out that mess.  You will waste a lot more time than it would have taken to download the images and put them on your own server.

I think that we can produce better images here.   I want BIG images that are often not available from the manufacturers, I want multiple or different views that are not available from the manufacturer.   I want optimized images that download quickly and look nice.

So, in short, if I have a choice between betting on me or betting on the manufacturer, I am putting my money on me.