Just out of curiosity--and I'm not being confrontational with this question or trying to dismiss your feelings--how exactly do you feel ripped off? I could see if someone was passing off a design/selling it as one of their own, but if someone gets that image tattooed on them, I don't really see it as the creator of said image being ripped off. I do understand that the tattoo artist is charging the person to tattoo that image on them, but they're charging the person for the work being done on them, not for the image itself. Now if a tattoo artist had someone else's design up on a wall w/o consent and was trying to pass it off as their own, then yeah, I could see where the feeling of being ripped off comes into play...but if an average Joe walks into a shop wanting to get an image tattooed on them, I don't really see it as ripping the artist off.
Now if the image is copyrighted and the tattoo artist still tattoos the image, then I completely understand where feeling ripped off comes into play...but if there is no copyright attached to a piece of work, there's really no way to enforce it.