It would be nice if players (or more precisely their nicks or assigned unique IDs) could have their global stats of all games they played (won + lost games) saved. The stats could be visible on a special page containing more information about every player.
There could be also a list of "TOP" users who played most games in a week, month, and the whole period since the stat recording started.
Players who would play (and finish!) e.g. 100 (200, 5000, 1000 etc) games would get a virtual award (or a badge).
Good luck at that. A type of points system in multiplayer was considered before, but it's far too easy to fake in an open source game, since anyone could see how "points" would be stored, and thus cheat. While we haven't had any issues with cheating in the past (to my knowledge), such a system which makes games more competitive, could lead to such. Not to mention the difficulties of finding a half decent way to store such without breaking it on new releases, new computers, etc... All in all, it just gets over complicated.
In special contests the best player could win a real prize (titi suggested "a real card" for Intel graphic card owners). 
The prize could be funded via Paypal donations.
Again, as per my reply on that post, you overestimate the community size. Good luck scrapping up costs, not to mention that the winner would have to indulge personal information to even receive the prize (I got an email from a Nigerian prince with a better offer, anyway).
