Welcome to the Forum, Stardusting!
With regards to challenges, for TS3 we had a Projects board, and I expect that eventually we'll add one for TS4, too.
In the meantime, if you're writing a story based on one of your challenges, it would go in Miscellaneous Stories, with a link to the challenge in your blog for the rules.
You might also be interested in the Forum's Challenge Tournament, an annual event that begins in January. There's a challenge team that devises the challenges, but you can send them a PM (private message) with one of your ideas. I would suggest looking over past challenges before doing that, to see if your idea has been done already. You might also be interested in entering the Tournament. All you have to do is follow the rules for the ongoing challenge(s) and post your score in the appropriate thread. The Tournament is more about having fun than winning, so it doesn't matter when you start participating.
