Right well lets start from the top left shall we, with ash right everything looks great here, this is indeed a very good and acurate sprite, the hair looks perfect and i know from experience ash's hair is a pain to get looking right :D the only thing I would say is with his cap, i would make it a front view as the cap only got turned when he was catching a pokemon, also the shading should be a darker shade of red as it blends a bit much here. All in all 9/10
Good old brock next, he is for lack of a better word perfect everything just looks like classic brock very nicely done, especially on the hair. 10/10
misty much like brock is pretty much perfect, so not much to say here :D 10/10
Jessie once again looks very nice, she is almost perfect but her hair looks way to big and a bit like an affro, so maby make it a little bit smaller. 9/10
James, much like the opposite of jessie almost perfect but his hair isnt long enough I know its hard to get looking right but it would look much better if you could. 9/10
Butch, perfect but maby switch his hair for james's I think that might look a bit more accurate. 9/10
Cassidy, once again the hair is almost perfect but again switch for the james sprite, and keep the pony tails of course :D 9/10.
Giovanni, is just perfect seriously it looks so much like him that its uncanny, make his hair a tad bit darker and then its just 100% 10/10
Good job here mate truely, but a recuring problum that I can see is that the pants are always only one pixel row accross i would make it 2 and add an extra pixel at the top corners for shape, that should hopefully fix the slight squareness that the boddies have here. Fix those few things and these will be by far the best anime overworlds that I have ever seen, so I expect side, back and walking sprites :D