When they're not on the clock, Alien and Predator get long just fine. When Pedro T. Predator decided to get a new piercing, Abi T Xeno was there to hold his hand. And when it was Abi's turn in the chair, Pedro returned the favor.
Pedro T. Predator (who is sometimes goes by the human name Mark), has some rather wonderful cosplay photos up in his deviantART gallery, including a few more with his pal Abi. If you prefer to keep your alien species separate, however, he also has some Predator-only pics, including one of Pedro proposing to his Predator girlfriend, Peyton. You can also more work from Abi, also known as the deviantARTist Rex-equinox, including photos of a xenomorph town meeting.
These particular tattoo and piercing parlor photos were taken by Kelly Clark.