How about not.
I think the best idea would be to have community member submit various content the ad workers could work with. All content would have to be polished (ie: events shouldn't be just what is necessary, but have decoration around it.) so that the ad workers wouldn't have to actually create any content, but just select what is coolest, and make Blockland look good. Also, you shouldn't get any prizes for getting your piece chosen. Think of the epic builds for v9, the fact that your piece was chosen should be gratification enough.