I ended up using the first fabric that I considered for the binding. At first I thought it was too dark and kept looking for something just a little lighter. I either didn't have enough or the color just wasn't right on all of the others so I was back to the dark brown with black lines forming little squares. I used a medium brown Superior SoFine thread to quilt it.
The back is made of 3 of the largest pieces of flannel I had left. I have lots of half yards but not much in big pieces any more. The quilt ended up at 64.5" x 80". I used Warm and Natural batting because it has scrim in it and stabilizes and gives body to the pieced flannel top.