I have a couple of tattoos. Each one has a very short explanation of what it is, but they have much longer explanations of what they are and what they mean to me.
The first one I got was on my upper right arm, of St. George killing the dragon.
If you are not familiar with it, the story goes that there was a village in Libya where a dragon lived nearby, and to appease the dragon, the people would feed it two sheep. If the sheep did not work, then they would feed it one of their children, chosen by lottery. One day, it happened that the king's daughter was chosen. As she was going out to meet the dragon, St. George came along and wounded the dragon enough to subdue it. He then killed the dragon in front of the whole village, and in exchange, they converted to Christianity and were all baptized.
The image I used comes from a book of Coptic pilgrimage tattoos, and when people ask me why I got it, I often explain that I studied Coptic for a year while I was in college, and wanted to get a tattoo of something from that book. I sometimes mention something about standing up for the oppressed, wherever they may be, because the Coptic Christians have been persecuted since the 7th century, when the Muslims invaded Egypt.
On a deeper level, though, it is something of a moral allegory to me about the nature of evil, and a theological statement. I want to call it an "interpretive schema," but can't bring myself to do that without feeling like I am talking out of my ass.
Our competing desires between good and evil actions are usually conceived of as being an angel on one shoulder, and a devil on the other shoulder. They each advise us, and we weigh out the advice. The way I see it, it is a little more combative than that: we each have both St. George and the dragon inside of us, doing battle with each other. The dragon is our desire to do only what interests ourselves, without regard for how it affects those around us. St. George is our impulse to do what we know is right, regardless of how difficult it is. (And believe me, doing the right thing can be a giant pain in the ass.) Our selfish desires can only win out if we are unwilling to confront them and fight against them. Sometimes that is as simple as suddenly remembering what the right thing to do is. Sometimes… it can seem as difficult as fighting a dragon. If it were a literal dragon, maybe we could think to ourselves that someone else might come along to kill it, but we are the only line of defense against the dragon within ourselves. You can either be your own greatest adversary, or you can be your own savior.