The message The artificial colors and soft focus give this image an ethereal feel, which is fitting for a shadow. It's an interesting idea, and it does grab attention to begin with; unfortunately, there isn't a lot of substance to hold it for long.
Creative choices The colors used here are well chosen, and keeping the trees black gives the image a grounding in reality. The texture of the snow is very nice. The composition isn't very effective; the image is divided in half with little to connect the top and bottom halves. Cropping off the top part right below the largest tree would avoid this.
Technical aspects The focus is appropriately soft. The exposure seems right, but I think making the midtones a little darker would show the shadow better and improve the image.
This is an effective semi-abstract, and the shadow is interesting, given the other elements that cross it. I think it goes too far in the direction of "computer art" and moves away from the essential photo quality the challenge says it's looking for.