Great 'playing' with lines here. It's a real shame that it gets a bit distorted because of head's shape.
The current version of the head looks nice, but i'd add a same kind of detail on the back as on the first version, but vertically. Also on back near the neck joint, there's a rather large black spot, so i'd add some line there. That little part looks quite bland, but i believe you noticed this one yourself already.
Nonetheless, this is pretty much the perfect example how simple can be magnificent, if artist knows what he is doing.