it's 256 so it's not perfect quality. But this is my 2nd hand drawn head and the other one just a little bit was drawn.

Any suggestions to fix it, other than the small seam in the back.

I just made it less blurry, changed the tones and fixed the nose

i would say just use a but of white to bring out some details,
like the stuff on top of the head just a bit of white to the center of them would give it some more depth.
use some opacity.