There are thousands of collectibles sitting in peoples star menu that would never be used, so why not invent a Collectible Hut, where they could be either converted into other, more use-able, collectibles like banners, etc or into resources other than stone or marble refills.
Some players, or maybe most, are always looking for ways to make better use of the collectibles we have, but never seem to find a way to use a lot of them.
There could even me a time lock on it so you have to wait a certain length of time before you could make the same exchange of collectibles as there is with the epic kill buffs like Rain of Arrows or Assassins.