Since even mentioning the concept of quests and specials rewards is now taboo, I decided to suggest something similar but not quite.
How about a system wherein you could earn stripes similar to the ones used by the military. A user could achieve certain milestones, as well as a single character, and these could be awarded by giving these stripes/ribbons. These awards would merely be ornamental and would not give any special bonuses. I think it might be kinda cool, and this was a fun way to waist 30 minutes so I made and example:
This could be a nice element on a revamped user profile page (I hear pixel sage is working on one, but I dont know anything about it.) There could be "hidden" awards that must be found, and others could be announced.
For an example click me!
The example page is merely a demonstration, the awards would obviously need to look more CB-esque.
/end Crazy idea