Just in case anyone is interested I found out how to set one wallpaper to span all 3-monitors. This will work with less or more as well. Each of my monitors are 1920X1080 to work on 2 I would use a wallpaper that is 2x1980 or 3840 wide and still 1080 tall. With my 3 monitors I needed a photo that was 5940X1080.
Useing the Control panel (W7 Pro) go to change desktop background, brouse for the photo select the one you want and set it as "Tile" as opposed to center or fit, etc in the picture position drop down. Since the photo is so large it cannot tile and spans the entire set of monitors.
Finding the wallpaper was a gift. Go to www.wallpaperfusion.com there you can search for 1,2,3 and 4 monitor photos. My search sent me to www.wallpaperfusion.com/search/?monitors=3 - And they are free.