I like the snow-covered look.

To improve it, you should consider doing something about the hard edges of the paths. I'm not sure how you have built your layers but I'd have done the snow cover with a layer containing a snow texture masked for the areas I didn't want covered...and then used a softish brush to back off the cover of the center of the paths and anywhere else I wanted the snow to be thinner or gone. I'd give the layer a style that included a slight bevel and perhaps a tiny drop shadow. Using grey in the mask (rather than black = nothing, white = full) would give you little humps and dips in the snow cover to represent drifts and variations in the underlying terrain.

I'd also soften up the bevel on the roofs. They're very hard-edged right now and you've also got the "ridging" problem that pops up when Photoship tries to bevel a straight line that's not at 90 or 180 degrees. I usually solve this problem by creating a layer filled with the roof shapes in white and then flattened to use as a layer over the roof texture layer...multiply mode usually. This lets me go in and paint out the ridges to make the sides of the roof look "flat". For your purposes, you could use it to smooth out both the "ridging" and the actual ridge line artifacts of the bevel...to make it look as if there's a nice snow layer.

Agree with Max on the shadows. Create a black copy of your buildings and copy it multiple times, moving each successive layer away from the building a bit more until you've got your shadow as large as you want it. Then you can merge them and use Gaussian Blur and set the layer on multiply. I actually get a bit more detailed and turn up the blur filter a bit more on each layer the further it gets from the building. Finally, if you want to get really fancy, you can paint in a bit more detail...to represent special things like an oddly shaped roof or a church steeple.

Hope any of this helps!
M