Firstly, I must say that the number of discrepancies that I have found in this skin is respectably low. That being said, the only improvements I was able to make were the following:
Improved shading on top of the head.
Improved hands.
Fixed discolorations in sleeves.
Made the stripes on the leg slightly darker for added depth.
Fixed the underside of the head.
Slightly darkened the bottom of the shoes.
Improved design on the front of the shirt.
Minor touch-ups applied to ears.
You can find the touched-up version here: https://www.dropbox.com/s/zr8zg4ljqbgxvf8/Mysticat_edit.png?dl=0
The improvements are very subtle, so you may have to see them side-by-side to notice some changes.