Well the deadline for the the swap is December 31st, so some people may be sending their little quilts after Christmas is over. I would think no theme or a generic winter theme is best for this one.
I have a few ideas in mind, and I'll wait until I get my partner and then "research" them, LOL. You'll be surprised by how much you learn from looking at previous posts.
With that said, if you are sending your quilt in November, and you know your pal celebrates Christmas, I see no problem in using a Christmas theme:)
Just my two cents.