Sven Sauer and Igor Posavec has a step-by-step of their “Dead Angels” graphic up on CGArena.  They used 3D Studio Max for the base modeling with ZBrush for the detailing, and it’s a great collaboration between a classical artist and digital modeler.

The Illochim (Herbrew: Engel) was here represented as an ancient race out of the depths of space. To create a different view on the misinterpreted creatures, Antoan Simic started first with the rough sketches of the chimera that gave birth to the legends of angels and dragons alike.

Making of Dead Angels – CGArena.