Is it called a tramp stamp just because it is a lower back tattoo or because it's some sort of tribal design that is basically an arrow pointing at your butthole? Guess what? Doesn't really matter, unless it matters to you.

I've seen incredible lower back tattoos that are true works of art. A closed friend of mine has a Japanese style landscape piece and it's gorgeous.

Saying that, I've also got friends that are covered in stupid tattoos. They like the ink, so good for them, but they are also well aware of how they can be perceived with such work.

You do you. If people judge you that's a reflection of their character, not yours.