I've quite a few friends with multiple tattoo's, and it always seems to be the people who get a tattoo just to have one will regret it. While the people who actually want it for a reason seem to always be happy with it.
One friend got a random tribal tattoo when he was 17 and has hated it since he was about 18, so he got it covered/replaced sort of with something about his grandad and seems much happier with it.
If you need to ask the internet for ideas, you don't have anything that has meaning and you'll probably regret it soon. Don't bother getting one just to get one, get one if there's a reason behind it.