Pleased you brought up the subject of paganism. The more pagan our society becomes the more people are tattooed.
But although vanity may come into it, I believe that it's largely to do with a lack or loss of identity. Think of how many children grow up today without knowing who they are because they have no knowledge of their fathers.
What Catholic, sure of his/her value in God's eyes, has him/herself tattooed?
A tattoo is the mark of slavery, or as someone else pointed out, cattle is marked by their owner with his brand. It is especially sad to see people permanently marked, especially on their faces.