Sorry for the late reply. I Definitely like the idea, and I think it would encourage members to post more. We would probably just give Flakes for the prizes, then they can spend it on whatever they want. I would say, 1st place gets 100 flakes, 2nd place gets 75 flakes, 3rd place gets 50 flakes, 4th place gets 25 flakes, and 5th place gets 10 flakes.
Since you are a staff member, I will leave you in charge of keeping track of who has the most points each month, then I will reward them. If you for whatever reason can't do this, then let me know.