I have a suggestion for a forum or sub forum. How about a test forum where you don't earn gold but where you can make a test thread. There you test out various things like thread setup, banners, posting style etc.

I agree with this completely. So we can test post formats, thread layouts and whatnot.

I feel a rather relevant suggestion would be a post preview option. That, combined with the test forum, would make creating an ideal format a fun and explorative venture.