About the only time you can get a good look at an interesting mount is to encounter it in the field, and usually that's just a fleeting glance as one passes by. or one happens to be in some town you're visiting.

How about reserving some space in the cities where players can mount up and show what they have, and others can see them as well? Most of the cities have at least one open area that's not really being used for anything else, where this could be done without the mounts cluttering the busier areas.