Iceblossom - your comments about design helped me identify another reason why I enjoy making "my" I Spy quilts. Although as Sewbizgirl said, there is a design element to them, they are also very in-the-moment and spontaneous - as long as you have pieces to play with, the only rule is that the sides need to add up correctly. Sticking with squares is easiest. For the second quilt, I found this great alphabet fabric that I wanted to use and I made so much work for myself when I decided I also wanted to have the alphabet read in order across and down the quilt. It didn't work to have them all in squares, so the rectangles happened which affected how I cut some of the other prints. I really enjoyed the challenge, but you'll see I migrated back to squares when the pressure was on again. It's also an easy type of project to do a bit at a time - there's little need to "remember" where you are in the design - just make the blocks then see how they work together.
I've looked at some of what people here are doing in the BOM/BOW/mystery quilt areas. I'm not sure I'm quite ready for this level of challenge (both in complexity and time pressure), but I've definitely flagged a couple of quilts/block patterns that I'd love to try one day. I'm putting out new little branches here and there, expanding my quilting vocabulary and production!