Since wow is a cartoon game, I think Ponies would fit as a race perfectly
Just think about the different ways to costumise them, different cutie marks that give racial bonus to your character, different manes, the posibilities are endless.
You can have Earth ponies, that have +mining skills, you can have pegasi ponies that have flying mount earlier, you can also have unicorn ponies with extra spell power bonus.
With them you can add a new planet named Equestria where you enter with a portal which turns you into a pony for the duration you are inside, we befriend them and they decide to join the fight after sargeras disguised as Discord turns all of equestria into a messed up place.
We the players can be forced to do dailies to collect the 6 elements of harmony to banish Discord. That to be the final boss of the Ponies Expansion.
