I've found some new neat mounts in the game files of the upcoming expansion.
At this time I have really no idea where they drop, but my wild guess would be that they will be rewarded through exalted reputation, Glory of Pandaria Hero, Glory of Pandaria Raider 10/25 versions and some may also land on the Blizzard Store.
I'll start with my favorite one - Green Cloud Serpent
There are various recolors of the same mount - Blue Cloud Serpent
Black Cloud Serpent
Red Cloud Serpent
Yellow Cloud Serpent