I think the idea of tattoos and body modifications is extremely old and especially common in nomadic tribal type cultures.
We have bones, needles, fine metal working, jewelry, brands, pigments and a pretty elaborate understanding of medicine as hearthlings...
So why not allow body basic body modifications in the game?
My idea is that it could be some kind of permanent or semi-permanent way to really set ourselves apart in a bit of a more real way than the simple character creation pool in the starting area. It could be a whole additional skill that requires understanding of medicine for sterility, painting for art, and relevant skills like psyche, lore, and so on
The idea would be that we could get 1 tattoo (or brand?) and 1 peircing, and that it would be like a permanent equipment that goes in the invisible aesthetic slots and actually provides us with some kind of bonus. Perhaps the location and pigments used for the tattoo would determine the stat bonus we get, and for peircing it would be the location and materials used. It would ofcourse inflict major wounds that would heal slowly over time or maybe need many applications of something like an ant paste to heal properly, but in the end it could be a way to uniquely customize your character visually as well as in a sort of "stat specialization" sort of way.
Just imagine the interesting possibilities, like having some tribal nose-bone piercing or tribal face tattoo that gives flat (or even small %??) stat or ability bonuses.
I imagine it being a earlymid-game sort of thing, having to build or craft specific tools for it and have specific stats for it to maximize the bonuses it gives and minimize the wounds it gives, both from the giver and the receiver (which could probably both be the same person too).
Many possibilities of how it could be worked out, from us actually knowing exactly what pigments and locations give what, to being something that we would have to experiment with over time and slowly learn as a community.
Over all, it sounds pretty FUN