In my teenage years the skull acted as a way to bring out a rebellious side in me and tell authoritative figures in my life to "stick it". Skulls were scary they belonged to the dead or those soon to be. They represented pirates, criminals and the lawless. Seeing someone with a tattoo of a skull instantly told be that they were a dangerous person.
It was not until I saw an image of David Dunlap including pirate flags into his art that I started using skulls in my own work. It was a way for me to communicate with the man in a strictly visual way. I started sending images I made of skulls and he in turn would send me new images. It is a fun way to communicate with a limited verbal interaction.
Instead of trying to verbally interpret what the other person is saying with their imagery, it is done using only visual cues. This has been an interesting form of communication that I hope will continue.