Cabin looks great, I love the textures especially the chimney stack, but the shape of the roof doesn't look like it would provide good drainage for the rain.
I don't know what the reference is but its hard to imagine a flat area where water and snow would build up and soak through the roof, so some kind of angle is needed.
Also it should extend at the bottom and front to provide some kind of eves, the shadows from which would help to better define the light source.
If however, you went with a change of light source to be more from right to left (before u draw heaps other stuff), you would get much stronger sense of form across all the shapes - just a suggestion.
At the moment because the left side of the structure still picks up a little light, it isn't a very strong impression and we have to use the clues to determine the source...