I 've mixed two shader a deep snow shader and a fakestonecomplex of pclavett to end up with this...
N.KAID
looks terrible.
The patchiness of the snow is cool though
Too little snow, too much rock for me. And I think it's not really seamless - there are render squares visible everywhere in the bottom! :( What detail/anti-aliasing is this image rendered with?
Did you try dandelO's snow shaders?