The ear is very straight and has no body or flow to it. One pixel diagonal left to the the bottom of the right side of the ear will make it fit the head properly.
The inner ear uses two random colours try moving it all over 1 pixel and changing it to the same colour as it's underside maybe?

I don't know but the eye needs to be re-done, try taking someone of similar sized head's eye.

I'm not sure what the protrusion on it's chest is but it looks slightly out of place, make it fit the body a little more, it also needs shading as it looks quite flat.

I can see you had a good try at custom shading on the body, it's decent however there is no natural look about it.
When shading it's beneficial to use existing Pokemon as a guide.

I like to use Poochyena because it shows exactly where the shades need to fall in every aspect including the tail.

Also you've inverted Chikorita's leaf to make into a head piece, genius but the shading is gone off when you inverted it. Snivy's leaf is lacking any interest as well.