I spy quilts are so much fun! I think the first time I saw the concept it was on a pre-printed fabric panel with hexagon shapes each having a different picture in them.
Anytime I get novelty fabric scraps, I cut 6" squares. I keep a small box of them, and when it is time to make an I Spy quilt, I select the ones I want. My I Spy quilts are "match" quilts with 2 of each image, and they go to Project Linus. Rather than sashing, I use a checkerboard design with alternating squares being all of one fabric.
I Spy quilts are fun to make when you have a child helping to pick out the squares and arrange them.
Dayle