Yesterday, after the ganking discussion, I started a blood elf warlock on a pvp server. I didn't get far, but I managed to get some apprentice discipline in before I switched characters. There it was, another polymorph I hadn't even recognized, and although I don't really want to be able to turn people into boars, it's out there as a possibility. I've been turned into squirrels, frogs, rats, chickens, even flowers. All of these spells are in the game, albeit as NPC abilities, and I think should be available to the mages willing to slough through the difficult task of getting them. The way I see it, the more variety the more chance for personalization of the character, and it sure would be easy to distinguish one mage's poly from another in raids.
Another idea on customization goes along with the concept of beauty parlors. Instead of having a lot of different animals, mages could quest for the ability to colorize their sheep. I've done it in other games, and this would be another way to distinguish targets. Plus, it would just plain be fun.
What do you think? Which animals would you like to see added to the list of polymorphs? Personally, I'm voting for polymorph: panda.