Ok, non-magical earthly "chocobo" alternative:
http://somoche.vtrbandaancha.net/Bernardita/Logo/avestruz.jpg
Appart from the earthly horses, we can only hope for giant versions of other animals if we want different mounts that have different roles. (why should i want an equivalent to the horse? I prefer to have other animal that can have a different role, be it a "tank", scout...)
-Horses: i cannot live without them. Well, i could if i wanted a truly alien world but they are still cool. Fast, easy to get.
-Giant spiders are mentioned in the lore i think and altough there is some magical "origin" to them, and being so common, they could be real mounts with added abilities like poison attack, web attack or good sprint/jump skill.
-Bears: Good speed, strength and resilience (not sure if it's a proper word).
-Tigers: Slow compared to the rest, pounce and some stealth.
-Giant Eagles/Hawks: FLY, very good scout, can break havoc behind the enemy lines (and not so behind).
-Lizards: I must say that i'm not so sure, they swim better?. For some are good choice so i mention them just in case.
Appart from those, i could only mention (considering that sea battles are nothing) scorpions (similar to spiders but without web attack and more melee oriented), wolves (i prefer tigers and/or panthers but wolves are just so wonderful... not sure about their role in battle though, somehow like tigers but faster and less pouncy), giant turtle (you know you want one tanking the enemy heroes while you fry them with magic from the wizards over it), giant mantis (like scorpions but without poison?).
And maybe not as a mount but as a weapon, but we should not forget about dogs:

Edit: i forgot to mention that i hope that Stardock adds some non magical animals of their own creation...