I had an idea for the site. I was thinking of what the equivalent of "free drinks" and "free rooms" (comps) would be for this site to encourage more visitors (bettors). Does anyone have suggestions?

Maybe a system where after a certain amount of BTC is wagered, your next bet will have a slightly increased payout. (i.e. 1.99x or 2x at 50% chance instead of 1.98x), or increased win chance for a given payout.  Obviously, methods that could abuse such a system need to be considered carefully. 

Anyway, just a thought.