are there any rules on starting contests or challenges?
This is a very good questions. While I do not believe there are any specific rules for starting a contest or challenge at CC there are a few guidelines I can suggest.
1) You need to plan it around the other existing contests/challenges that run from year to year. At this point you are looking at running into the annual Micro contest run by Robinhood, and the CCC will be starting again sooner than you think. As well as Josh is currently running a year of challenges, the moderator secret contest, and the CCC may be quickly followed up by a contest Aliencat and I have run for the last two years.
2) It is always best to run an idea past an admin, in advance.