It’s beautiful! You know I have to respond about something that has to be matched and sewed…. I would take the piece with me to a store that has a lot of quilting supplies, as I think you’ll need something that blends and supports the scene rather than calling attention to it. Usually, a person has to unfold a piece of fabric along side it to find the right match. I doubt that the wide binding that can be purchased (or at least used to be) would be the right thing. It would be a bit trickier, but you could also make binding that is cut on the bias if it has a subtle design, but something that might be creative and pretty. I was thinking that a piece with the blue, brown and gold in your picture in a very small print might work….