CnC time -
recommendation 1
make the part underneath the chin only slightly darker then the face itll translate to the sphere better
recommendation 2
keep the marking on the head above the highlights
instead of highlighting over them take a thin brush and highlight the edges of the lettering brighter then the main highlight

other cnc
the nose seems too bold to me at least the tops of the nostrils

good base shading

i enjoy the feel your going for behind the mask

Cheers man ^^ It didn't turn out as chiseled as my sketch - something I can work on.

I think I understand what you're saying about the highlights and the markings, but I feel that if I try to do it now I'll just make it worse XD

You're talking about the nose being too bright I guess? I kind of like it like that ^^