This head is just way to all over the place. The style you're drawing with changes from each piece you do. The bits for the eyes are really detailed, but the the grey circles to the right have no details at all. The piece to the left has horrible pixelated edges on it.

Just kind of sloppy work so far, and with what you have done I just can't really get a feeling of unity from it, just feels like a bunch of stuff that wasn't meant to be together.