I'm thinking, the images of the pokemon from the 3 series of games, and also from the cardgame, where available. So if we take Pikachu for example there would be the RBY image, the GSC image, the RuSa image, Base set Pikachu, most of the other set's pikachu, Birthday, Flying and Surfing Pikachu, etc. I know that's a lot of pics for just ONE of the many pokemon, but I would certainly like for it to have a great variety and uniqueness to it all. Then there'd be the humans from the tv show, and so on...
Personally, I'd like the pic of Scizor from the TCG, the one from the Neo series, with FalseSwipe as it's first attack. Love those wings...