These are really good. ^^ I would have used more shades of shadows and highlights, but they are just as good without that. I noticed that the shading on Skitty's tail is kind of awkward - the areas should be more curved, if you get what I mean? ^^'
It would look better if you spend more effort on the backgrounds.
Here's a tip (; Why don't you use the bezier tool? (the curve beneath the A) It makes the lines smooth and nice, much better than the pencil.
But these are really good, I love Skitty's leaft ear. :3