spinny heads are shit.
so far, the back feels empty and there is a seam at the back. feel free to tell me to fix things.

lol nice hero

Great work hero.
as you said the back is plain but Im sure you can fix that.
the front is very nice. the complexity of the shapes and proporsions is very nice.
I am greatly anticipating the finish of the top and back.

fix things.
there done =)

looks sick sofar.
im guessing your gna do something with the top front part?

Yea, or at least make the skull bone thing more detailed.

texture it in like a subtle fusion between front and back shading? horizontally

cranial joints and fontanels ought to do the trick also, love the eyes babe

Mang thing is gross.
Quick Suggestions:
-give the top bone plate thing some texture and form(it'll help hide the seam I bet)
-darken the shadows where the bone plate connects with the ridge for depth(the thin line outlining the ridge is too graphic and cartoony for the style)
-pop out some highlights on the bone ridge
-I'm not sure how the front of the boneplate connects with the flesh of the face because of those midtones

this things going to be sicknasty when done. It looks all Resident Evil samurai. Nice work.