Just as a general hint on the subject... a contest design thing is pretty good, however when I first read this, I was thinking that more than a random theme would have to be submitted... I mean, a theme is a theme, not an 'idea' really... and definately not a contest design.
Good contests consist of a task at hand, not a theme - "design a nuclear winter game" is much much different from "create a game that revolves around special system designed to help survival in nuclear winter", which could lead to something as the radiation-level-displaying Pip-Boy from Fallout 3 (taking an existant example in case the nuclear winter theme wins... don't want to spoil any contestivity). This way, there'd be an objective to reach, and results would be more interestingly compareable; and you could say "okay, a radiation display is cool for survival, but there could be something more actively helpful".
However I'm not trying to get anyone down or say the contest won't be a cool thing... just saying what I'd like to see in the next installation of this (if it turns out any successful) for feedback reasons. In that sense: Have fun!