The design looks good and the line art looks good. It's a cool character overall. I think if any, improvement could be done on the shading? I don't know much about shading myself its something I struggle with very much. I like how the shading looks on the hair. What kind of art style are you going for?
Anyways I'm not good at giving advice but here's a suggestion on what might help:
Find a old drawing. any drawing, maybe something you don't like or something you feel like you could have done better on. Keep it saved or hidden somewhere. If its traditional you can keep it safe in a sketchbook. If it's digital you can save it in a file and make a copy of it and email it to yourself. But don't look at that drawing for at least a couple weeks. How ever long you decide it up to you. Then after a couple weeks you take it back out and redraw it. It's a method that I think helps artist improve...it's certainly helped me and I've done it many times when I feel like i haven't been improving any.
I don't know much about right art or critique. Overall I like the character and the style you've got going on. Keep it up! You can do it!