Maybe some more textures would be needed to have a well made snow level. There are very few for a well-made level IMHO.
I can take inspiration from UT series, there are great snow levels there. (DmTundra
from Unreal; AS-Overlord
from UT; DM-Flux2
from UT2003/4; ONS-Dria
from UT2004 and WAR-ColdHarbor
from UT3 for example)
Also, a shader which resembles falling snow flakes can be nice as well.