If you find scenes on a stockphoto site that you would like to use, they have id numbers. The print shop quite possibly has subscriptions to these sites and will download the images. Of course its easier to talk to your shop to see who they can deal with. That was the procedure the club used when we contacted MO GRAPHICS in New Lenox. Kevin there guided the selection process.
After looking at 10,000 'Chicago Panorama' images, I found nothing that was exactly what I wanted. Thats when we got the photographer and got our own images that MO Graphics was able to print and mount. We now have about 110 feet of photo backdrop.