i think i settled on the type i want. Unsurprising, i decided to go with Australian aboriginal body paint. I have a soft spot for Aboriginal Paint (actually own 2 piece in my house, which i'm very proud of).
here's a few example of what i got in mind (and white is actually a nice idea i think). This also help reminding me that this kind of body paint is different for each one, despite the fact its using roughly the same style or geometry.
On this picture, what stuck me is the far right guy, on his legs. I wouldnt go with something as extreme as this (well, it could be an idea if i want to make a Hero/Lord out of a normal guy).
Something quite simple, but still very effective. Dot like these could be easy to achieve, and i think the final result could be very good on the scale of orcs.
Lastly, different pattern, that prove that it can still be made and looks like part of a "band", as long as it use the same technique.
Good news is that if i decide to go these way, i could also paint my banner in the same way (if you want to know what i mean, google "aboriginal dot paint").