I think as long as you don't want to have WoW logo or Blizzard on your arm i think you can take any faction logo and put it as a tatoo, i mean, its just a symbol, we recognise it as a faction, when other people will see it, they will just say 'nice tatoo, what is it?", of course you can anwser two ways
a) Geek way "oh its a world of warcraft faction, you know the orcs i have a 80 lvl one and i raid...."
b) normal way "Yeah i know, i love it, its just a symbol i saw in a game(or say tattoo shop) and decided to get one"