Version 5
With Version 5 I added some dynamic lighting. I used a projection lamp for moving cloud shadows. That's the effect I've been looking for to create ambience.
To make the shadows I baked Blender's clouds onto a torus. It's a lovely cloud ring, for fans of Rocket Science's OBSIDIAN. Unwrapped, it's a periodic texture. The cloud ring is so pretty I'd like to include it in the age, somehow.
Of course, dynamic lighting brings new challenges, as can be seen.
Oh, and I accidentally erased the second cloud layer. I like more blue sky so I'm holding off on restoring it.