I'd look first at creating the artwork in Illustrator or Photoshop. Maybe you could get your tattoo artist to sketch up a few samples. Then work on revealing the artwork, possibly on body parts using the same techniques used to reveal line drawings or signatures. There are a ton of tutorials available on that subject.
The other thing I'd do right away is work on a budget (time or time and money) for this part of your project. Opening titles can take a huge amount of time and just looking at your initial description and my suggestion I'd say there's at least 80 hours work in a modest title sequence with these techniques.
Search for dripping ink and dropping paint effects. There have been many tutorials built over the years to help you learn how to do simple reveals or complex flow and fill simulations that ca totally creep you out. You might want to vist The Art of The Title Sequence site, too for extensive interviews with artists who build titles for features and how-to deconstructions of their work. Creating a title sequence is your chance to engage the audience but it's not necesarily where you tell them anything about the rest of the piece.