Hmm, mapping seems well done, good job having straight lines at the top.
What I do dislike though is the mouth, very edgey.
Shading needs more attention too.
Not too bad though, I'd rate it 5,5/10.
"i rlly want to join it cuz to me it is famouse" ~woodysaad
Personally I like it, you've done the shading well and the lines are made superbly. As the others said I don't feel like the mouth fits with the rest of the head, It needs to be more simple than what it currently is. Other than all that I would rate it around 7/10. Keep it up mate, it's looking great.
Life is like Basketball. Aim, Concentrate, Balance and Following through. That's all you ever need to accomplish your goals.