24 hour RPGs are really driven by theme and ideas. You don't have time for much innovation or trying to sum up all your years of playing in the prefect rule. A list or competition like this is a great help to newcomers and those who haven't really tried the effort before.
Choosing from a list of ideas doesn't bother me the way having some ready clip art or notes would. However, you can at least wait until your time starts to chose a topic, rather than picking one and starting the game when you find the time.
For the purpose of contests and drawing in people, this sort of set-up may be a necessary evil. If you're making a 24 game by yourself, well then be as strict as you feel is honest.
Finish the game, and feel good about yourself - that is what matters in the end.