That head is really underdeveloped for what a 512 head texture could look like. To my understanding you are fairly new to texturing, no? Try to lower your dark outlines to a very small size, just used to seperate the segments of you head, I'd also recommend working on shading, since you don't have much here.
I do like that your head does actually look pretty damn good, though. It has a general flow to it and it's not ugly at all. Good job, duderino.