I was drawing a few maps this weekend and I've been trying to figure out how to make a winter-like map without leaving big parts blank. What I attempted this time is to use a light blue color and then up the contrast so only hints of it popped up here and there giving the white starkness some sort of texture. While I think it succeeded in some ways and my best (and only) attempt, but still needs some work to get it where I like it.
I used a couple of 'green' islands in the snow to help with the difference. Next time I'll play with more muted colors.