looks like you got lazy on this one.
top and bottom of the head were completely ignored, doesnt affect the sphere much, but makes the flat look boring.
agreed with the lower teeth, dont know what you were thinking there.
mouth design in general doesnt look thought out.
nose is too wide.
circle on the forehead should have been mapped correctly like the ones at the back.
the spikes/horn things at the back are all copied, pasted/repeated and are cartoony/flat.
sides are nice and grungy, while the rest is all smooth gradients. need to be consistant.
lazy use of the pen tool on the sides/back area.
probably my least favorite texture from you.