I love the cat's design! The mint, white, and dark gray/black goes nice together (reminds me of thin mints or mint-chocolate-chip icecream, lol).
The first thing that stands out to me is the front legs. The anatomy seems to be wrong (not that I'm great at cat anatomy). I'm pretty sure that cats' legs have more joints than shown. The front leg that's further from the viewer is sticking out oddly, while the closer front leg is very stiff. The back legs are really nice, though.
I think it's a really good picture. You should be proud of it ^.^