Hey Dreedo, I think that would be fine! In fact, if your religion has its own holiday during this festive season you could make your game about that if you like. Feel free to be as creative as you like, the rules are pretty lenient. Try to make the kind of game you or some kid you know would like to play at this time of year. It could be a snowball fight game even! Or a Snowman Maker
While I write up the post for this year's competition, have a look at last year's rules and see if you think they sound reasonable enough. I'll write a little more detail about how the games don't have to be directly related to the Christian holiday.
And for some ideas of the kinds of games that were made for last year's competition, have a look at http://amigachristmastree.ultimateamiga.co.uk/
I only just realised there's only three weeks left so this competition is going to be shorter than I had hoped.