This was a concept for Smaug that I had put forward early on in the Design phase. I had been thinking along the lines of Smaug potentially having a boney structure on his head to smash and burrow through tunnels under the mountains he resides in. Thus you'd see many broken bits of his hardened face. I'm so glad they went for a more classic dragon design in the end, but it was fun to have a play!
These images can be found in the book "Smaug; Unleashing the Dragon." They're very small images in the book so I thought I'd post them here so the detail can be seen.
This first image is a close-up of the full body piece