Change your illumination: You applied light in the left contour of the snowman, followign his shape. In some cases this is OK, but in others, this could lead to flat appareance. Try applying light in a more volumetric way (search 'shaded sphere' in google)

 

Dare to use blue shades on the floor: If you search for pictures, digital art o even cartoon series with snowy landscapes, you can see they GENERALLY use a combination of white and blue shades to depict the snow (or ice) and even mountains. 

 

Keep practicing!