Hey, my last attempt at contributing failed, so I'm gonna have a go at helping you pimp out your bank alt
So first off, the best bank alts are mages and I'll tell you why in a second, so make a lvl 1 mage of the race that you think looks the best.
Second, run to a main city like Orgrimmar, or Stormwind or the Undercity, just somewhere where you can get a mage to port you to dalaran.
Once you reach dal, go to the violet citadel and buy Tabard of the Kirin Tor from Archmage Alvareaux at the top of the stairs. Now, the reason that you're a mage is because mages are the only ones that start off as friendly with the Kirin Tor, and you need to be friendly with the Kirin Tor to be able to wear their tabard.
Finnally, you should purchase the Tuxedo set from either the AH or have someone make it for you.
I know this isn't that helpful, but I haven't contributed anything since last year, and I've taken so much, so if you're bored, try it out, I always get people asking me how I'm lvl 1 and have a tabard that mostly only lvl 80s have.