I have tried a few different fabrics for the background and have finally settled on this rather unusual yellow/green pin dot from Riley Blake.I stitched one together to get a better idea of whether I liked it or not:
These two photos below were taken as the clouds were scudding across the sky and despite major wind gusts. I'm nothing if not persistent! I laid the centres that I have already made on top of the blue one so I could see how it looked and get a photo. You can see the change in light - even though I was only outside for about 5mins in total!