I have been experimenting with three different ideas.
Old ceiling tiles, which I have checked do not contain asbestos, very scary idea, which cut and shape very easily, painted white along the edges. These I have used to create larger areas of snow field and smaller snow drifts, sort of.
I have also used some old terrain I made for a club I used to run many years ago, as small ice structure terrain. This stuff was originally a kitchen work surface which I liberated from a skip :-)
Finally I have had a bag of white sand knocking about the garage for years now and with it I'm trying to make some small scatter terrain pieces, although I'm not convinced by these two, I think they need rounder more organic shaped bases.
Also I have a load of blue, white and green glass beans that I want to use in one way or another. So we will see how it all goes.