Thugstructions (AKA More Improvised Items Suggestion)

[Xenonia]

Tattoos would be fun in theory, but I think it'd be pretty tough to get anything legible to fit onto a body part on the mob sprite. Arms are only about three or four pixels wide. At best I can sorta maybe see a splotch of color and a modified description upon Examine for the player working, maybe.
This is Jay Wolff! He has a pretty haggard tattoo of a skull.

That's kinda the idea for arm ones. Maybe have a small symbol for chest ones and head ones though.