I sent Intmon a message last week indicating something like this where the member in the spotlight would receive a free item from the AO store. Just as a way to promote worthwhile contribution through positive reinforcement.
This sound's like a good idea. Have a monthly "Member Spotlight" and like you indicated, have that member recieve something from the store. Good thinking btw mathgirl and nice idea Angelic. This type of thing would make member's contribute more to the site (or make them contribute positive and knowledgable thing's).