After getting the idea of what the piece should be worked out with him, I started sketching thumbnails, eventually getting an approved shot like this:
Where the Elite aliens are gathering together one last time before shipping out to war. Alien spacecraft are launching in the background to head to the front lines.
I created the background when I had sometime, before heading into the harder work of the characters themselves.
Some time passed before getting back to the piece, and when I did, I felt that the shot was too far drawn out to really capture the emotion of the characters - the most important part of the piece. So I cropped in close, stretched out the background to fit, and started reworking it. I sketched the Elites out first on paper with pencil, then scanned it in with my large-format Brother MFC-6490CW (college graduation present-boy is it helpful!). Here you can see the piece with some base colors thrown into the sketches.
After getting some feedback from Bry, I revised a bit and then started in with the details, trying to perfect every centimeter of the piece, from really rendering the characters to detailing the background and the spacecraft.
I'm particularly found of the sky. It turned out beautiful, I think. Definitely not what I had started out trying to do - it just happened in the process.
Here's a little experiment. I created a basic little video to show the rough draft fading into the final piece...