I think the issue with the hat is that it seems flat and a bit off from the perspective of the rest of the piece. Thinking of the hat brim as an ellipse, it needs to be a bit narrower, and thinking of the top part as kind of a deformed cylinder, you need to show the body of the cylinder, whereas you've only drawn the top, so it looks squashed.
I also agree the eye should probably peek through, even if it's only the white part. Good work finishing off the ATG though; I just submitted my final piece too! *brohoof*