Well I'm currently working on some Red sprites that needed cleaning up/replacing Hilbert, bout halfway through (walk/run, bike, item and save poses are complete). Not doing the dance sprites though, seems pointless. By the way Supagokuman, did you ever consider using the Blue sprite from B2W2? He also has his own battle animation too...which is another thing you need to think about for Blue/Gary and Leaf, although I have no idea if the battle animation sequence (Bianca's bouncing for example) can be replaced with a different one.
For the other region gym leaders and champions, game freak didn't put in full overworld sprite sheets for them
http://spriters-reso...nw2/sheet/48049, only the very basic ones, so you'd have to make the rest yourself if you're wanting to use them. The animations can't be replaced with new frames as such, as they're all broken up like the pokemon sprites -->
http://spriters-reso...nw2/sheet/48033
However it's possible to make your own animation frames using these sprite parts, as I have done so already and the result is great (It takes a bit of time to get them right though)