Blizzard recently released the Armored Bloodwing mount in the Blizzard store. I don't know about you, but I've seen quite a few out in the wild, with some of them just hanging around big cities, showing off. This mount is not quite to my taste -- I'm a huge sparkle pony fan -- but I like its aesthetic and I see the appeal.
Other than the Celestial Steed, I also bought the Wind Rider Cub plushy and in-game pet set. And the Spousal Unit has the Winged Guardian mount. (I think he's eyeing the Armored Bloodwing too. Hmmm. Father's Day is coming up ...) In addition, we each have the collector's editions for several years and all the pets included there.