We have seen skull tattoo designs before and it is not very uncommon, but I bet you never saw a snake skeleton. These two look like partners from Hades. Remind me of Cerberus, a monstrous three-headed dog guarding the gate to Hades and ensured that spirits of the dead could enter.
Read more about Cerberus and related tattoo designs.
Read more about Cerberus and related tattoo designs.