Rebel Angels was built in a vector art drawing program called Adobe Illustrator. You lay down what are called Bezier points, which are attached by lines, and these define the shapes. It's quite different from photoshop.
Here you see the underlying structure being fleshed over with the final result as a mask is pulled back.
Came across some more wonderful artwork depicting this set of miscreants. It's fabulous stuff, riffing off of the Louis Le Breton originals. You can find those here.
A print edition of Rebel Angels is being solicited in this month's Previews. Head on down to your local comic retailer and order the book and make my dream of printed pages come true!