I just finished my first Tunisian project, the Crochet Chunky Tunisian Cowl. I decided to search other stitches and the shell stitch was so wonderful! I started using a smaller yarn but decided since the stitch was a lace stitch, I would use the 10mm hook still. This was also mainly because I wasn't at home and didn't have any other size hook.... and me waiting until I got home? No way! ha-ha
I found this Tutorial on YouTube that shows you how to make the shell stitch.
Here it is on my sweet boy.