High resolution version available here.
The products are fairly easy to get. The Microballoon filler is commonly used to cut resin to make lighter casts, and it is a very fine powder. Try not to kick it into the air and inhale! The Snow Base is part of a Woodland Scenics "Scene-a-rama" set that includes base, snow flock and some icicle making lacquer in a little paint jar (the kind GW includes with their starter paint sets.)
Interestingly enough, some of the samples changed dramatically in the 24 or so hours between creation and this photograph. The Vallejo Foam Snow sample shrunk, and the Woodland Scenics Snow Base cracked and separated more, although the snow base might not have been adequately mixed for that sample. Some of the microballoon samples lost volume as well.
Overall, I was most pleased with the simple and cheap mixture of PVA and Woodland Scenics Soft Flake Snow, either just mixed together or mixed and topped with more Flake Snow. The PVA + microballoon mix probably looked the most like a fresh fall of snow at a small scale. The simple PVA topped with Flake Snow would make a good frost cover. Some of the later samples were topped with a mixture of Flake Snow and microballoons to see if the surface texture was dramatically different than using just one or the other, but I don't think the results warranted the trouble. The mixture of all the products led to some different textures, and I would assume that those could to roughened/smoothed with the addition of more of the wet component.