The SKULL as a Symbol

There is hardly a graphic icon that symbolizes death and mortality more than the human skull.  A dead body eventually reveals the bony structure hidden beneath rotting flesh.  This is horrifying to humans on a visceral level.  The skull's morbid associations are rather easy to understand.  What seems odd to me is that so few see the skull as a symbol of anything other than death and decay.
For me the image of the skull is a reminder that there is something hidden at our core.  In a way the skull is evidence of the secret, unseen person - the real you- and as such suggests our spiritual nature hidden behind a facade of flesh.  Because it is the hard structure upon which our muscles, tendons and skin are attached it symbolizes (for me) inner strength.  The bones remain long after all other body parts are gone so it is a fit representation of the inner self, the true self that survives death. 
There are alternative perspectives.  Here's an article that offers diverse cultural views: Death's Head Symbol.   While you're at it check out another link that suggests other ways to think about skulls: Skull symbolism.
In my own magickal workings the skull carries a very positive meaning.  It embodies the center of the mind and, therefore, the seat of spiritual power and consciousness.  Adorned with the symbols I inscribed on it, the skull engenders the qualities of the various spirits and deities that are significant to me.