I would like to use a shop keeper image to make my user shop look less boring. I'm posting here because I want to make sure it is okay to use images around the site in our shops.

I know for overlays you're not allowed to use official art. Maybe it's the same for shops? Have you checked The Rules? You can find them in the teeny tiny font at the bottom of every page.

Yes, and I couldn't find any mention of it. I will look for a different image until I get a solid answer. =/

The only issue I can think of would be possible confusion with an official shop if you're also using an official shopkeeper image? Maybe it's best to make a ticket for this, then staff will be able to give you a direct answer. :)