It's okay, I guess. I suggest you change a few things:
1: Instead of making Aaron's hair the "hat", try to cut and paste a hat from an existing trainer onto his head it make it Santa-like. Or, better yet, try to scratch a Santa hat. If you never scratch anything, you'll never improve much, since you'll be limited to only using existing stuff. And since you can't use stuff made by other people without their permission, you're going to be poorly limited to using only D/P/P sprites.
2: It's winter. Try scratching some sleeves or something onto Aaron. Or put a jacket on him.
3: Frakenspriting, perhaps, instead of using only one type of trainer base?
4: The shading on the shirt's a bit odd. Even though it is a D/P sprite, try shading yourself.
Just a few things you can take into mind if you want to redo the sprite. If you don't want to (since it is your 4th attempt), you don't have to. The 1st and 3rd suggestion can help you a bit in your future sprites.