I've made Indian/Arabian style tattoos with it, the first one was made for me by a Somalian girl when I was in high school, picked up my technique from her. I've also dyed my hair red with henna("hue" is an understatement). Haven't done it in a few years now. It's differend kind of henna you use in your hair though, and it's pretty permanent in hair, so don't do it if you aren't sure you want to be a red head.
EU is planning on bannig the stuff/decided not to ban it after all, I'm not absolutely sure. That's because animal testing showed some carsinogenic tendencies. I think that's ridiculous, the test was made by feeding some poor rats piles of henna. I'm not planning on having any for dinner, and I also wonder, what would have happened to the lab rats if the scientists had fed them say, L'Oreal hair dye instead?
I suppose they wouldn't have lived long enough to get cancer, but I don't see anyone banning these kind of dye. Hooray for multinational business power!