Yeah, I know. I should have read it before making this. 

I'm not sure if you've read it, but cure's tutorial has a skull shaded properly if you want to use that as reference in fixing this up a bit.

Here's the address: http://www.pixeljoint.com/forum/forum_posts.asp?TID=11299

 Thanks,  I also think the lightsource is the big issue with this one. I should focus more on that with my next piece.

I like how it is not just mirrored even though the perspective is straight on. It has a nice sad look and good details. I think the reason it looks a bit flat is because there is no apparent light source. I think it would be much improved if there was a clear light source from an angled direction.

I dont know, It just lacks solidness or depth, if you know what I mean. (I am not native english) The skull looks more like a mask than a solid object to me.