Almost every other type of armor in the game can be dyed. And with more really awsome backpieces coming out im sure im not the only one who thinks they should have the ability to be dyed too.
The majority of the upgrades or things people work toward in GW2 revolve around the ability to customize your character to look how you want it to look. For example the holographic wings, i think, would look really freakin cool if you could dye them to match the colors of the rest of your gear. Not to mention it would make them see much more unique to the character they are on if you could customize them to your own liking.
Just wanted to throw that out there and see how many people would like to be able to dye their backpieces