What I have noticed while looking at the many factions of the mod is how underpowered the Taurethrim are. Boasting only 3 types of combat units, weak armour and isolation from many other factions means they are pretty weak compared to most other factions in the mod.
One of the biggest problems with them is the lack of any mounted units. Even their neighbors, the Morwaith, have a mounted variant of their main warriors. The simple answer would be to mount them on some kind of equine, however due to Far Harads affinities for having strange mounts I am going to suggest something a bit more out there.
Located in South America (the same place as many of the cultures that inspired the Taurethrim) where the great terror birds. Being the top predators of their ecosystems, the terror birds where alive during a time when the largely isolated South America was finally connected to North America. Even with the competition with the saber tooth cats of North America the terror birds where one of the few creatures that spread north on the newly created land bridge. Sadly these creatures died out before the first native Americans arrived in the new world meaning no one got to see these great beasts.I suggest a relative of these terror birds lives in the jungles of the Taurethrim and became their mounts.
The terror birds would be similar to a horse in size and a bit more heavily built than most other birds in the mod. They would most likely attack the player if provoked and would naturally attack the flamingos similar to the lions of the savanna. Though only the speed of the average vanilla horse these birds would make up for there speed in manoeuvrability. They would most likely be able to fit through 1 block wide gaps which would make them more useful in the thick Jungles of Far Harad. They probably would not have the best health, around a ten however could be given armour to help them survive more brutal encounters.
Taurethrim Warriors would sometimes spawn riding terror birds and use Taurethrim pikes before switching to a sword or dagger once the Terror bird has been killed. They can be hired for 70 coins from a Taurethrim chieftain at alignment 350.
Thank you if you have read this far into this suggestion. If you want to criticise something in it please write it down in the comments. All criticism is encouraged.