Apart from the mounts, there are various NPC models apart from Thrall, some of which have surfaced already, some of which haven't. Velen, Grommash, Durotan and Blackhand are all there. There's several varieties of Iron Horde machinery that have been found, as well as some pale orcs, new Talbuks and Sporebats which we heard about following the recent press event, and Elekk, Goren and Hippos. All of these come in a variety of colors, so do check out the original post for more info.
But my favorite new model by far is the Draenor Ancient. Like all the models, he's in a variety of colors, but look at his grumpy face! What has you excited from this recent datamine?