Here are some possible choices for Clockwork mounts. My choices are mostly skeletal and Heavy Metal looking mechanical beasts to match the brutal nature of the Iron Horde's adaptation to this new technology.
Easier to control than an out of control Devilsaur and twice as deadly. Mass produced, midless and perfectly mimicking the primal nature of the former beasts tortured and processed for its creation they are only one of many fearsome creations of the Iron Horde's arsenal. No other mount could demonstrate the synergy between the Iron Horde's new technology and lust for battle.
Haven't seen this idea catch on to blizzard so I figured I'd throw this poll out to see what you the people would want to see. Personally I'd be truly disappointed if Blizzard didn't put this in after giving us mini Mech-Scorpion mounts.
Mechanical War Horse
Iron War Wolf
Iron War Wind Serpent
Iron Devilsaur
Iron Star Mark 2 (Spider Tank)