Isengard has wargs
Humans have horses
Goblins will (I assume) have spider riders
Mordor will be having mumakil
Dwarves will be having? a guy in a cart like from BFME2
Now im wondering....What do people think of "Ram riders" or how its called in the movie (The hobbit: Battle of the five armies) "Goat riders". I personally think it would be great to see the dwarves have some more cavalry abilities. And I think it would be kinda fun to see the hero "Thorin" for example climb some rock part cus he is mounted on a goat. Ofcourse it is all speculation but I think there are some great options there...since in BFME 2 shellob was able to climb around entire mountains

Im not saying it HAS to be in the game...but I believe it can be fun if it became part of it.