The couple forums I have been working on to get stuff setup in advance for, has a few features that I prefer to give to people who contribute the most to the place. A few features similar to what would be expected for a VIP membership, and a couple of other features that are nice to have.
Rewards only mean anything if it's an active forum and there is traction. That's like getting top poster of the month on a forum where you're the only active member. There's no meaning to it.
Mine at the moment doesn't have anything set up right now to reward members who contribute to the forum but I am looking into ways I can add things into the forum that will allow me to reward them for their contributions to the forum as I feel incentives sometimes help with activity on the forum and who doesn't love rewards? 😀
I think it is best to offer a reward system for people that have contributed to the growth of the forum. It is a way of showing you appreciate them and many others would be motivated to do more to help the forum.