It's been years since I've taken Latin. So I don't know that I'd be much more accurate than google translate. But if you are looking for good mottos in Latin that are excellently translated, check out:
http://www.yuni.com/library/latin.html
The fact that very few people know Latin these days means you could put a joke up there for sheer amusement and no one would notice except the few who can translate and then I'm sure it would make their day.
Braccae illae virides cum subucula rosea et tunica Caledonia-quam elenganter concinnatur! Which means: Those green pants go so well with that pink shirt and the plaid jacket!
There are a lot of other fun ones but also quotes as well. I'm not sure its on there but I want to get "ego sum qui sum" tattooed somewhere. It mean I am who I am.
I also asked a friend who is a Latin major. I'll let you know if she does it.