Thanks so much for your response, Nalates!
I haven't logged in yet today, but I will look into that. However, that doesn't explain why a plain white texture still doesn't show up on the left arm. No matter what the unwrap is, it should still show up white.
I tried this on the basic system body, and Slink Hourglass. When I try anything on Legacy or Maitreya, the textures glitch in various places when in Edit Appearance mode. Testing a tattoo on them is near useless.
I'm doing all this with Bakes On Mesh, though I suppose I could try with Omega testing it. I'd rather avoid all the HUDs while I'm working, though.