Thanks Tony. You've been a big help and didn't even know it. I did exactly what you describe above, but the image didn't show up in the background selections. Just for giggles (and because I trust you to know what you're talking about!), I changed the aspect ratio preference selection to 4:3, and...BOOM, there it is! So I went to Paint.net, changed (cropped) my image to 16x9 and saved it in the 16x9 folder and sure enough, there it is. (I learned something about Paint.net, too!!)
So thanks very much for your help.
KK