This project was done with the old LuxBlend addon, so it would be a bit of work to install this with an old Blender version just to check the materials.
If I remember correctly, the snow shader is a glass material with lowered opacity and homogeneous volume (with high scattering scale, something like 100). The snow particles are a bunch of randomly deformed low-poly icospheres. I applied them onto the model with particle collision (die on hit so they stick, and render dead particles).
The hair is part of the background photo. Only the mask is 3D.