I know that there are already monetary rewards in place for half completing and completing a dungeon, but I'm more of a practical man. I enjoy exclamation marks over heads and goals to work towards if i'm to go traipsing around with multiple classes.
Would it be hard to implement quests for each and every dungeon for completion? I love those little flavour texts attached to each one, and flags are an amazing incentive.
The current 'read the patch notes' way of informing players that there is a reward is up for grabs seems a little lacking in typical QCF whimsy for me.
Probs too late now, but more permanent and memorable rewards than paltry gold (feh, gold *rolls eyes*) would be great too.