You might find some in logs of people that had tattoos, which makes finding out some progs pretty simple.

Here are a few basic examples of things you'll see though- and there are lots of probably way more specfic ones.

Lots of damage type things and other automatic in combat progs.
Various prep type things- usually not automatic. (+ hit, +dam, stats, whatever.)
Then there can be other Invoked progs that might be combat based or not.

I know quite a few specfic ones, but you get the idea. Also, keep in mind, not all tattoos will do everything, I think an immortal has control over what a tattoo will do for a given character (they can juice them up or take things away as they see fit)

Hope that helps a little.

And feel free to delete this if I said too much or went too detailed, I'm not sure if this is supposed to be more of a hushed thing.