Dearest Professor...
I didn't mean to cast any aspersions as to your fine moderation and passion for the contest, Professor. My apologies if I hurt your feelings. I am quite familiar with contests having done quite a few in various places on the web and I have found that if you want to get people to participate there has to be some direct communication with the artists. Using the PM service here in BEArchive would be an excellent way to invite artists. I do know quite a few artists here, but there are probably others that know many more than I do and I don't know if it my place to invite artists in your contest.
As for different ideas for contests, you might consider more anatomical categories instead of categories attached to a scene or object. For instance, a contest featuring very large areola, or pendulous breasts or side or rear views, or large nipples or lactation or breasts that come to the hips or navel or whatever size or perhaps even different shapes of boobies - pear shaped, football shaped, stretched shapes, high "bimbo" implant like breasts or breasts with veins or stretch marks - or even nipple placement high or low. Perhaps others have ideas that they would like to see art done for?
Again, I am just making some suggestions and I appreciate all that you do and the time you spend for the contest. Thank You...!
Lel