Just to chime in, I definitely agree with Neo and the others about the separating lines between topics, and I do prefer the book thread markers to the generic circles. I also agree that 2 & 3 just feel a bit generic and "blah", but I do like Tuxagon's mock-up of the default theme without background textures. I would be curious to see one with the background texture only on the darker/outer "base layer" background - it might still add a bit of character without seeming too dated.
If I had to choose strictly between the three as presented, though, I'd go with #1.