Was thinking last night while i was playing that i dont really drop my banner so often and would like to see my design more often. I thought it would be a cool idea for tabards to be visibile on the characters back so we wont have to see our ugly armors. I wouldnt want it to have any other purpose other than it being aethically pleasing and it would probbably be better to have a toggle switch to put it on and off similar to MP power in our option menu.
To be honest, I think it is already hard enough to appreciate another characters outfit in the heart of battle, given the amount of spell animations in group play as it is. In a way, being able to design your own chest piece essentially feels like a nice enough idea, but I don't see it being a feature we are likely to see until expansion where they may consider the idea of 'guild support' where I assume tabards is a tagged on feature, or maybe added on to the achievement system where you can earn them based on completing certain adventures within the game
I think it would be too much of visual clutter, I could see a colored ring on the base of the characters feet (right now it's light blue or something, it could have colors to differintiate the players from eachother)
If you play a lot of multiplayer games, you have banners dropping left and right every couple of minutes when your teammates are calling out elites, goblins and mini-quests. Will still hold in 1.08 for players wanting to pinpoint their locations or as pre-warning notifications.
In addition, there have already been announcements that there will be some sort of armor transmog system in the future, so that will solve your "ugly armors" situation.
FYI I happen to like how my Zuni Marrow looks. Though I did hide my Mempo, Vile Ward and gloves.