Hey that's not a bad idea perhaps mini challenges need to be redesigned. Models that are simple and defined as to what is expected.
This would be my suggestion.
There doesn't need to be an end date on challenges because we could do something like Facebook's Like button or +1 from google. We can post one topic about once a week or two and users can always submit to that challenge in hopes of getting the most amount of likes. It would be a running challenge to hold the most amount of likes for the longest time.
I don't know the specifics of creating such a thing for the SM forums but I cant imagine it would be that difficult. There has to be tuts out there for creating it. If SM is interested I would be willing to help figure it out.
We could even try and do groups like
Small non-organic: "Challenge 1: Barrel - Wood, Metal, Open, Closed Your Choice"
Vehicles: "Challenge 1: Past Buggy - Horses not included
Vehicles: "Challenge 2: Future Personal Transportation - Single rider futuristic design
That's just a few ideas
What do you think?