From the Burning Crusade bestiary:
Warp stalkers are crafty, predatory hunters indigenous to Draenor that have been corrupted by the Burning Legion. Some reports even suggest that Legion officers employ the stalkers as mounts, utilizing the creatures’ uncanny abilities to phase in and out of the physical and astral dimensions at will. Unbound by the constraints of physical reality, these powerful, mystical creatures often range far and wide: almost no realm is out of reach.
Warp Stalkers, or perhaps their uncorrupted form, are a strong possibility for Draenei mounts.