I got the great oppurtunity to work on the shells for the main characters during the development of Way of the Turtle. We needed three different shells for the special powers you learn, and variations for leveling up. I started with creating a bunch of designs in Photoshop and after a few rounds of feedback we landed on the final designs. They were then sculpted in Zbrush, modeled in Maya and textured in Photoshop. It was a fun challenge, and some shells took longer than others to get right.
Turtle model by Dennis Brigelius at Illusion Labs.