You've got to be kidding?! I'm sure the first thing a passenger wants to see is a freak show in the cockpit. Why not go for some of those spikes the yabos stick through their heads - at least you know with them that it's not damaging their IQ any.
Seriously, this is a conservative profession and you need to look like what the public expects an airline pilot to look like - and that doesn't include making a freak out of oneself. Try the merchant marine if you want to do the tatoo thing.
