Not sure how big each panel is, but I think I would make what I call a 'borders' quilt. All borders around the panel; the fabrics you show with the panels are perfect for that. Each of the horses will be like a framed jewel in the center of the quilt. I've done that several times and they turned out beautifully. I usually start with a narrow first border - in this case I'd probably start with the center fabric, and make each subsequent border a bit wider. last border would be the running horses, and i would put some kind of what I call a corner stone block in each corner.
Another idea that would probably turn out great is to use the horse panel as a medallion, like I did in this quilt. The bars at the top and bottom of the quilt would work because they could be made to look like fence posts. It does use a smaller block for the medallion, but I think one of these horse panels would make a great, if somewhat larger, medallion. have fun!
http://www.quiltingboard.com/picture...d-t271149.html