For being finished, it lacks a lot of polish. I suggest adding more highlights and some darker shadow tones as well as antialiasing some more of the areas that don't have it. Something I noticed is thet you have some antialiasing on the 45-degree part of some lines, particularly in the shoulder, and you shouldn't antialias those as they are smoother and better looking wihtout it.
I suggest reading up on antialiasing while you're at it; the aa color should go about halfway down the line it's antialiasing, but on the hat and various other areas it's a single pixel, leading to jagginess.
