Ok, this isn't exactly a vanity pet, but I felt it was worth mentioning because it just sort of caught me off guard: Pandaren Dragonling. It's an engineering on use trinket that summons a Pandaren Dragonling to fight for you for one minute.
First thing that came to mind was a black and white (panda) themed dragonling.
WHICH WOULD LOOK RIDICULOUS. But awesome!
I can just imagine a fluffy looking, panda colored whelp. LOL! But it probably won't look like that and instead will likely look like an "asian-themed" whelp from panda-land.