I was browsing through the creature archive on Wookiepedia, looking for creatures that would make great creature mounts, and I found these two:
Krak'jya
Jaggalor
They're both lovely, wonderful, good-looking creatures, both are already in game, and both would make great mounts to ride into combat, as both are known for their predacious savagery.
Therefore, I would definitely be willing to venture a guess that they would both be great sellers.
Simply put, I think that these two creatures would make all-around great mounts, and awesome money-makers.
Thank you!
Hail and farewell,
- ScorpioStrikes