I don't think we know - it's been the subject of mass fannish speculation as to whether he gets them put on or whether they show up as evidence of his power as he gets stronger. I think the evidence pointing to Renji just being an ink fiend is that the kid who idolizes Renji, whatever his name is, got himself an eyebrow tattoo in emulation. And I don't think we've ever seen Renji's legs, so we don't know if they go all the way down. (I have to admit that I know this because I've spent some time looking through the tags on bleach_fact, where people go to ask questions like that. Answers not guaranteed, though. XD)

Report back on Togari! I've looked at it, but haven't bought it yet.