Hmmm, I like the idea of having these kind of little quizzes, just don't think it would be appropriate to do this in the Polaroid picture above. It would be a bit weird to have such a thing on the home-screen, imho.
But it could work to create some kind of quiz-section with these kind of games. We could even implement some kind of leader board system. After all, we all like to play games on this forum, don't we...
Now just find the spare time to implement such a thing...