I'm 15 & I Want To Get A Tattoo?

No, I don't want one now but when I'm in my 20's =). I was thinking about getting either a little star with a cresent moon on the left lower side of my back, & it's not gonna be big but it's not gonna be so tiny you can't see it either. Is that still considered a tramp stamp, & is it a good idea? Give me your opinion.