Never really thought about this before, but upon watching it animated, it just seems.. wierd. I mean, we've seen half a dozen other Bankai activated, and none of them change the user at all. And yet Ichigo gets his swanky Zangetsu style coat and Renji gets his fur cloak, baboon skull shoulder pad and tooth necklace. Very cool and all, but why only them and no one else? Only thing I can think of is that maybe it's something that happens the first time you use Bankai, and thus all the experienced captains dont change appearence? Or is this another of Bleach's "just because" things?