I did this drawing years ago, but then only recently inverted the colour to create what you see below, I like the effect of the shaded drawing being turned inside out, so the dark areas become white and the white background becomes black.
The skull art is something that I am specializing in more as time goes on what with tattoo designs that I am concentrating on together with graphic novel ideas that I have.
Skulls have that simplistic design and you can place them into other drawings as great central design elements.