I saw a group of pictures of nerdy tattoos yesterday, but I can't find the link. There were pictures of maybe 50 tattooed people with things like DNA, Darwin's drawings, physics formulas, and chemical bonds as well as a few famous lines from great books. There were no tattoos related to economics. Then I did a google search on economics tattoos no luck.
A search of Supply and Demand tattoo shows that Peter Leeson author of The Invisible Hook: The Hidden Economics of Pirates has the curves tattooed on his bicep (From Economists Do it With Models)
I'm not really into tattoos but if I had to get an economics tattoo, I think I would go with a set of indifference curves with a budget constraint.
Lucky for my family my indifference curves on the two axis of tattoos and nontattoo goods intersect at no economics tattoos.