That is a really cool quilt. We took a fall trip to Northeast Iowa a couple of years ago and I was so pleasantly surprised at all of the barn quilts we saw. Later discovered there is actually a small tourist map that shows a route where you can see many of them. It is a beautiful area.
But, I don't really have much in the way of quilting suggestions, other than SID around your picture blocks to stabilize them and then go from there. I usually look at Leah Day's website where she has posted more than 365 designs for FMQ on a home sewing machine. Lots of inspiration there! Daystyledesigns.com