Ice and snow flocking is another descriptive word for a search.
A white or light cream throw rug, or other cloth, like towels, a sheet, tablecloth, curtain, under the fleece would help "color fill". Maybe provide a decorative boarder too.
Snow piles and snowballs....Packing styrofoam in layers. Kinda like rock sculping except I rolled little balls off each pile or trail instead of cutting. I wasnt sure it would work at all, and I never got around to paint and glitter after. The camera is pretty cruel; it's hard to see the spherical grains in person especially in the colored lights. Paint wouldve helped.
Alternately, it makes a good base for covering with fleece or batting and providing a firm surface for structures and figures. Sinking some figures, trees, and other stuff ankle deep in deep 'styro snow' helps them stay standing 
It takes a while, but you'll likely find enough "perfect" balls to make a good pile, from "carving" each snowbank if you're supplying a snowball fight.
