How would you SEO this page?

Dear Sam & TB:
Thank you GREATLY for this in-depth insight. I was aware of that aspect, but wanted to run this by you (see link) in which I had that covered. If you click this link to a sample page, click any thumbnail which opens that same image to a larger version, accompanied with pay buttons to my shopping cart. That page offers a tab reading “Cartoon Details” and directly underneath that is an actual description of the cartoon plus the actual written caption below that specific cartoon.
I did extensive data entry regarding this, and all 5000 different images throughout the site have had this same data entry added for each different image. Now, my next real question is whether or not this was a waste of time (which took me ages it seemed)…