also I think if "Success Stories" is the main focus then this contest is limited to very few people coz majority of users here are new to being forum admins and have forums not even an year old. Not all have/can have 2 million posts with 1000 users online. I hope this is what you mean by a success story.
Why not make it a "Best Article/Tutorial" submission contest instead that majority would like and find useful. It can be any topic whether success story,
seo tips, graphics creation, programming, etc. Then you/your staff/polls can chose/vote for the best out of them.