If you do machine embroidery, you'll find lots of options. You could embroider different cowboy images on different parts of the quilt.
Have you googled "fabric + cowboy"? I just did, and fabric.com had a number of nice prints you could work with. In fact, you could probably put enough together to make an I-Spy quilt if you included neutrals for lattice and/or alternate squares.
Have you seen the Disappearing 9-Patch pattern here for making an I-Spy quilt? It's marvelous! I'll do a search and post again.