I began working exactly as I had done with the previous thumbnail, creating an impressionistic view of the scene. This time I decided to keep things subtle, less saturated and less sharp.
I blocked in the jagged peaks of hell and then sharpened them up with finer strokes and hints of backlighting. I also added some sillhouettes of sharp peaks fading into the misty chasm.
There was still a lot to add, but I was a lot happier with this attempt. Although it appeared less eye catching than my previous effort, the mood was exactly as I wanted it. It appeared more lonely and isolated and the background was subtle and wouldn't steal attention from the characters.
I still had the choice of adding in lava and a tower, trees and other such features, but this could wait.
My next step was to resize the thumbnail to my working size. In this case I chose to work at 2500x1500 at a resolution of 300. Ideally I would have worked much larger, but my CPU isn't fit to handle many layers at large screen sizes so I had to work within my means.