Blizzard really does seem to have finally realized that can give us a few more decent ways to save space without breaking anything or trivializing the game. The new vanity pet and mount skill system has done wonders to clear up bag space on my characters on Beta, and I just can't wait to be able to do it on live.
Of course, there's tons more stuff that a good, solid pack rat can keep in their bank to take up space, from cool looking quest rewards to old gear sets to tabards. Tabards are an especially massive space investment. Even with just the basic battleground and unique event tabards, we're talking at least half a good bag taken up in the bank, and that's with deleting all the easily re-obtainable tabards to save space.