Brian,
Leaving him with non tatoo removes you a challenge in painting. It is up to you to select an appropriate tatoo figure, but I think that with such a large arm, it is a normal challenge for a painter to decorate it.
If some of them have no tatoo, we expect in our mind to see them been tatoo'ed, even with a Mickey Mouse, Asterix or their face only!
Use diluted indigo for this after full drying of the oïl paint ...
(not: I do suggest, but I can't paint free hands myself, and I m busy to impose me also a tatoo on the arm of my next flat, at smaller scale!!!)... Hi! hi! this is for September for me ...