I like the list idea.  For the challenge,  the mod can suggest or even call the theme..afterall,  it is to be a challenge!  Or list a few possibilities and in a limited number of days folks get to choose with the favorite getting the nod that month.  For each to suggest an idea does seem a bit cumbrsome.

We could alway have a thread only for developing a list of possibles...get a bunch done in a hurry. I would put a time limit on this thread to encourage early suggestions.  Then again, I am not the one who has to do it!        Tom.