Hey there Daalex
NO REF? Interesting you have NICE muscle defintion and theres definately talent here. As far as anatomical crits, the ears on mice (and most all small animals) are a very thin, yet slightly rigid (sticks out not flappy like cloth). In fact as you can see in this pic, light passes through them (transluscence) they are soo thin. Its also quite round, not pointed like a cats, which is what the shape of you're looks like.

Now don't take any of this too seriously as you are obviously taking some creative liscense (cartoony a bit). But i'll keep going, the hands are going in the right direction, and this pic may also help with that, and just so you know the back feet look most excatly the same.

Keep going with this man and good luck to you.
Oh and sorry about the blurry pic i cleaned it up as best i could in photoshop (found on a google image search)