I'm just finishing my third I Spy quilt, two were for the granddaughters, one for the youngest grandson. What kind of fabrics were you looking for? Did you have a particular theme you wanted to use or just any boy themed fabric?
I started collecting 1/4yd pieces. I bought fabric from Hobby Lobby, Hancocks, Joann's and even some from Walmart. Found fabric with dogs, some paw print, SuperMan, some that pirate ships, and some John Deere tractor, baseball fabric. Just went through the fabric stores looking for things that were something a little boy would be interested in, still have plenty to make quilts but it was fun collecting them. Bought Superman fabric from Walmart for the backing, and it absolutely was the best fabric for the quilting stitches are so hidden by the busy print! On this last quilt, I repeated the fabric blocks several times scattered around the quilt. It's so busy with prints that you really have to look hard to see the repeats and I turned them to go in opposite directions so no matter which end you're looking from, it's right side up. It's amazing how after all the blocks were sewn together, they all go together. It certainly wasn't intentional but the primary colors are dominant.
Let me know if I can be of any more help. Take care, Chris