After much deliberation on this one, I have reached an answer:
The ideal location would be the left forearm, but my Timon tattoo, whilst not exactly in the way, has a tail that loops around and creates interference. Consequently, Jedi Mario might end up on the right forearm, giving my right arm a 4-2 lead on the tattoo scoreboard. Then again, Mario could end up on the left upper arm. There’s technically room, though the forearm has long been my preferred option.
If he goes on the right forearm, then the next tattoo will be a sonic screwdriver on the left forearm. See, it’s all mapped out!