These maps could have been used for snow displacement, but I did some tests and it took a bit too long to render. Maybe it needs more optimization; I'll give it a try for a future project!
The map for the field and road in the midground was painted in Photoshop, as I needed something specific for this part of the environment. In the background I used a satellite view grabbed from Google Maps and edited in Photoshop (contrast, color correction, adding and suppressing some details here and there). Same for the mountains in the background, with a different map (Fig.14).
Lighting is a single mental ray sun and a plain blue Skylight. I did some test renders with HDRI maps, but wasn't really satisfied with the results. There's also a warm colored omni for the farm (Fig.15).
At first I tried to use some photographs for the sky, but none of them really matched what I wanted in terms of cloud shapes, colors and lighting. So I tried with Terragen 2, and after a lot of time experimenting with the many different parameters, I got the desired result (Fig.16 - 17).
I could have painted it, but it was a good opportunity to test the possibilities of Terragen 2 for skies. The final sky consists of two 2k renders assembled in Photoshop, as there is no panorama export option in Terragen. I used a wide ratio to adjust it freely in the image composition (Fig.18).