I created a mapping challenge entry with lots of floating ice. You can find it here: http://www.cartographersguild.com/ma...break-ice.html

It includes layer styles you can set up in Photoshop (I don't know if there is a comparable feature in GIMP). Hopefully that will help. Post #6 has lots of info on how it works.

While I'm posting, I'll add my 2˘ by saying I like the white snow, or a white/blue snow. Snow can be like sand dunes where you see the effects of wind. A google image search of "wind on snow" or "snow aerial" might give you some good ideas or textures.