Fairly simple suggestion: More color customization options for body parts
Additional locations: Nipples and Genitals.
Details: For the nipple and genitals could simply use the same colors available for the characters mouth for the most of the color options and a 4 to 8 brighter / more exotic options (Examples: Radioactive Green, Metallic Gold, Electric Blue, Royal Purple, etc) ... while I think about it the additional color options could also be extend to other body parts as well.
How: Options during character creation and an option at the tattoo shop.
Effects: Allows the creation of a more visually unique character.