I suggest you try studying anatomy a bit more. It doesn't really look like a skull of a person as of currently. The eye sockets seem to be too high up, and the same goes for the nose-hole (don't know what it's actually called).
On the topic of bones and skeletons, I remember making this four...
So this is the first sprite I've ever actually finished in a long while. It's a crystal turtle and his name is Bob and he likes to make stuff
If I ever become un-lazy, I'd properly get around to making more and starting up a new thread.
Metals are highly reflective and will mirror any surface you put it on.
I remember making this study a few months ago. It basically goes shine > base color > shadow > base color. It's bright, become dark, then becomes bright again.