Now that has been something that's been wanted by players for a long time. They introduced void storage and you can put some in there, but some you can't even place in there because they're unique. Right now I sell all the tabards from WotLK and Cata factions, because I don't have enough space, and I can get them again if I wanted to. But if I really wanted to wear a tabard here and there, I'm not gonna go back every time and buy it. In the end I just barely use any tabards because I dont want to carry them all with me, and I need the space in my bank for other stuff. I really hope they get back to the whole idea of a tabard closet where you can select your tabard in a menu or something like that, similar to how titles work. And make it account-bound.
Blizz has stated the only thing holding them back from doing this are tabards with clicky effects. Once they solve that a wardrobe feature is an easy addition (assuming there aren't more important things they would rather spend their time on).