Hey dude, i wont be harsh, but i will be bluntly honest if you like.
For one the texturing is really off, he looks as tho he is wearing lip stick. Here is a good tutorial for painting human skin:
It’s written for Maya and Photoshop, but the techniqes are transferable.
But lets leave texturing aside for now and concentrait on the model itself. Could you post a shaded shot, as well as a wireframe, and from both front, side and 3 1/4? This would help alot in seeing what you have done with the model.
It looks very low poly, is it meant to be, like for a game? If so then its not too bad. But if you are wanting to go for more high poly and realistic shape, you probably should follow a good head tutorial on head modeling.
Personally i model my heads via the box method, which i find allows you to get things like proportion early on in the modeling stage, but this method is equily as good.
For what i can see, the bridge of the nose is a little wide for what appears to be a caucasian person, it should be much tighter and sharper.
The shape of the eye needs more points to be rounded out properly, as well as pulling the eyes inwards where the sockets would be then rounding out into the brow and cheek area. You also need a few lines around this shape to create a proper eye-lid that has a rounded shape of its own.
I cant really see his lips through all that lipstick, but you need to increase the amount of cleft that runs fron the middle base of the nose to the middle of our upper lip. The lip shap itself should have a tight lined border that starts the lip area and is rounded inward in the mouth.
His cheekbone area is pretty flat and smooth, you may want to both bring the cheekbone area out as well as pulling in the cheek underneath, just slightly tho.
The eyes should be modled rather than just have a jpg wraped over them, you should be able to find a tutorial on the construction of a 3D eye. This will yeild a much better result.
I would sugest also rotoscoping your mesh over a good front and side shot photo of a person, this will help you easily nail the features and give you a good idea of what goes where. Also you should look at wirefraimes of other peoples models that turned out really good. You should be able to find a heap of thease by doing a images.google.com search.
Anywayz, i think iv said enough, i hope some of it helps you out.
Blend on, and blend well!!!