This head is amazing you've put a lot of effort and the smile makes the head rock.The side burns are good i like the way you added a pattern.I think you could make some textures so like a ninja or something and sell this as a set.
The Shading was Nice..
Lower the Ear will be good..
The Big Smile looks funny.. but the Nose too Small.. and i not to like it..
The Eye was great.. and a nice shade there.. 8/10
and goodluck for the Set..