The dark green head is very clean.
What you could have done to make it better was to fill the whole mouth showing teeth. Towards the left of the mouth you put black. Although you did it to show and angle of the face it doesn't fit well. It looks like his mouth is from a side angle while the eyes are at a straight angle.

I do like how the head looks but since the eyes are at a straight looking angle, the mouth should match it.