I don’t know if it’s the best way, but it will achieve what you are trying to do.
Use collections. Create a new collection called Background Images. When you create the background image, it will show in you file browser. Put it in you new collection.
Now pull up an info panel. Toggle the background image off. The image toggle will show you the python code to toggle it on and off.
Now this guy shows you how to use that code to make your own custom button which I think you could tie a hot key to. https://www.youtube.com/watch?v=IUkofDrGd9o
