What are the standards of the people playing? If the average time for a game is <10 minutes then you might want a different structure to those who aren't so quick at finishing. Also how serious is this meant to be, if it's a group of mates then I'd probably just do a round robin style as below where everyone keeps tally of wins and losses.
One fairly obvious way to do it is split into two teams of ten, so each player gets twelve minutes per game for the first hour, then pair off the top five from table one to the top five from table two for the second hour and the bottom five from table one play the bottom five from table two at the same time. Final half hour is for the top five from the "winners" group (who at this point have won two games each) to have a brief knockout tournament across the two tables.
I'm sure there's a better way of doing it as some people won't play each other at all and you'll have some waiting around/drinking time for the losers towards the end but that's my first thought.