Potential Cloud Direction

I really like the way the clouds are done in 300. They used a series of compositing tricks to mix watercolor and coffee stains with actual clouds, creating a surreal effect. We might take a similar direction, probably pushing the watercolor more (as in the graphic novel).

I did a test on this image from the movie to see what the sky would look like if it were blue.

This is a test of mixing different elements through compositing. Instead using of real clouds as in 300, I found some cartoony ones and created some blotchy paintings in Photoshop. It didn't turn out quite as I had hoped... but it's a basis for discussion.