The newsletter that these images came from gave us a few scraps of information on some mount mechanics. There will be temporary mounts for rent, aimed at lower level characters, and riding into water will throw you off your mount. Similarly, you can be shot off your mount if you ride into battle (though no word yet on whether mounted combat will at all be possible). Missing from any of the concept art shown was a mount for the Dark Elves. The newsletter promises more details soon on mounts in general, and perhaps we will learn about their mode of transportation at that time.