Ok, so this is a nice example....
When you're uploading a photo, PLEASE PLEASE PLEASE RE-NAME IT TO SOMETHING ENGLISH!
This file was named: 1022-1404745607-cats20142222photographoftourcompanybyalessandropinna.jpg
Now, that contains useful information including the 2014 date, that it's the tour, and the photographer is Alessandro Pinna. But the useful information can be held on the photo's page, as seen above in the description. If you're editing a page, being able to pick up the UK14 Jenny 1.jpg link is immediately obvious what photo you're referring to. As for categories, it belongs in "Images of Jennyanydots", and "Images UK Tour".
Part of what I like about Wikia is that we can attach all this information to each photo. I'd say this is the best result for a photo, in that it contains all the information we could want - actor, character, production, photographer credit - We can't access all that information for all the photos we have. But if, when you're uploading photos, you can add as much as possible, it'd really help!