This.took.me.ages

Firstly I'd like to complement you on the expression on his face, as you were able to make it very clear that the boy is angry or annoyed at something. Also, the overall picture is quite pleasing to the eye and I can see you put a lot of work into it.
Things you could fix:
- add an eyebrow, it would help express the look on the boy's face
- hair usually comes out of one place somewhere on top of the head, so all the hairs should start there, the shading should also be at the parting
- add one/a few white specks to the eye - that would be where the light is reflected

I hope this helped ! <img src="e.deviantart.net/emoticons/s/s…" width="15" height="15" alt="" data-embed-type="emoticon" data-embed-id="391" title=" (Smile)"/>