I have heard of a tournament in the US where the prize is all of that year's unclaimed lost property and was thinking of doing the same thing at this year's Christmas event (between the Iron Man and Keith Loveys).
What do people think about making the format a Reject Rare Draft - each player would have to provide 45 rare / mythic rares as their entrance fee, these are then randomly made into 15 card all rare "repack" boosters, which are then distributed amongst the particpants and then everthing continues like a normal booster draft.
In this instance anyone that would receive a prize, gets to pick an item of lost property (they have to take the item away with them or dispose of prior to leaving (it can't be "re-lost" for next year.