The bits of grass need some help - the snow under them is a different color white than the rest of the snow. That white should probably be changed to transparent. And you may want to make the grass itself more of a brownish green instead of turquoise, since it kind of clashes with the shadows under the trees and bushes.

I'm not sure what's going on around the right edge of the shadow under those trees.

And the top edge of the trees at the bottom of the screenshot is really... flat?

Trying to make a decent snow forest using only recolored CT tiles does sound like a challenge. The way you did the treetops and bushes is pretty interesting and looks good.