What will the next collectible thing in WoW be?

I have a transmog collection I’m constantly working on: farming old content, trawling the auction house, running dungeons and raids. Other people do this too. Still others run around farming for rare battle pets, or trying to get that one mount that they’ve always wanted. Some people chase achievements to collect a certain number of these mounts in order to get more mounts. All of this is fun for the people who engage in it, so I’m not complaining, exactly. I know folks who are desperately filling up the toxbox on their collection pane just because they love those crazy widgets and what they do.

But what could Blizzard add to World of Warcraft that people would have the same obsession with? Some other Blizzard games like Overwatch have sprays, but those don’t seem applicable to WoW. Diablo 3 has cosmetic wings and pennants/banners you can wear on your character — would that be something WoW players would want? [Editor’s note: yes.] Or is the next collectable something entirely different, perhaps? We talk about player housing a lot, but to my eyes player housing’s biggest value add would be all the trophies we’d collect to spruce up our new abodes. Ah, and think about the furnishings! People would go nuts running old dungeons for a throne like the one in Blackrock Depths or Blackwing Lair.

What do you think? What could the next collection be?