This 2010 TEDxUSC talk by Johanna Blakley is well-worth watching, if you're interested in the sharing culture, creativity, and copyright.
Description: "Copyright law's grip on film, music and software barely touches the fashion industry ... and fashion benefits in both innovation and sales, says Johanna Blakley. In her talk, she talks about what all creative industries can learn from fashion's free culture."
Length: 16 minutes
Since this video, I think the thought around the copyright on tattoos has changed, although likely there is still a lot of sharing of designs by most tattoo artists.