Hmm... I think it's looks quite good what was your intention? Or rather what an art should it be? Is it like you wished for?
You colored it very good I think. You used shadows quite good. But the collar looks a little bit strange.. Sorry, I don't know how to say it "`_` A little bit like it don't fit, like you didn't take your time, a little bit like it's unfinished.. You see, difficult to tell you what I mean ^^;
I hope you don't hate me for saying this =)