This panel sample comes from David Petersen's Blog. He is the artist for Mouse Guard. He is a nominated artist for the 2011 Eisner Cover Artist and his book is also nominated for Best Anthology. If you're not reading this book then you are crazy! It's beautifully drawn and the mythology he has created is amongst the most fantastic worlds ever dreamed. Go, NOW, and pick up a graphic novel of Mouse Guard! Seriously, get going....
He has provided this sample on his blog site to explain his process and thought for square format. Strathmore even has a 12X12 bristol pad made available to comic artists... Even though this format has only been used in his books and the Muppets. Great horizontal layouts though! It provides a unique cinematic feel, the dynamics are balanced and the eye isn't pulled through the book with traditional comic format. *I'm not knocking it ,but his book IS nominated!
Check him out!