Skull and bones can symbolize not only death but immortality as they last longer than our bodies. Archeologists now find well-preserved skulls of people who lived many centuries ago. If you want to stress this symbolism of immortality you can add a snake to your skull tattoo. A shake that goes from an empty eye socket stands for a chthonic god of immortality, as well as knowledge. This symbolic depiction is well-known and tells us that knowledge remains after death.