I've thought of another idea for a Event where u can win a card, something along the lines of "puzzlemania"
I found this site, so you wouldnt have to create all 400+ cards (or however many there are lol) into puzzles yourselves.
Play thousands of free online jigsaw puzzles on PuzzleSnap. Browse by category, try the daily puzzle, or create your own custom jigsaw puzzles from any photo.
im-a-puzzle.com
The participants each would get 3 cards to solve puzzles from, (different difficulties), and if they would be the fastest overall they can choose one of the 3 cards to win, they would obviously be randomised by the cards/event team but maybe one of each batch?
You do however need a google or facebook account (not to play it) but if the way the site works, if you click on share and pro-option users have to enter their name and you'd be able to see the time they solve it in.
There might be other sites too for this kind of stuff, just an idea I suddenly had.