I think that the proportion of the ears needs to be a bit more inline with the rest of the face (unless you are going for that elfish look )
Try also to define the basic shape of the head so that it is not so even, it just feels a little too round at the moment.
The part where the nose leads into the eyebrows needs to become more detailed and accurate. By having the eyebrows continue on from the nose makes the face seem too long. If you lower the eyebrows a fair bit and make them not continue on in one line it might help the facial definition.
Try extending the chin just a touch, at the moment the proportion is slightly off. That's probably the biggest flaw of the model at the moment, proportion. Try finding some nice reference pics or even take some photos of friends etc.
Thanks
Alan
Technical Director - Framestore
Currently working on: Your Highness
IMDB