Some of the models aren't great so I did have to do a little bit of supplementary modelling/sculpting to get a more natural look.
I started out really trying to push for interesting angles and lighting using just a grey base shader. Here's contact sheet of all of them.
After I'd played with lighting I dialled in to one look that I really like and started working more on textures and materials. I did actually end up tweaking the lighting slightly but the overall look is similar.
Software used:
Maya
VRay
Nuke
Photoshop
