Yes, set it to 100% x 100%
You might have too temporarily move the viewer to access it if it is also 100% x 100% so you can access the Properties and then replace it once done.
Thanks for the response. Exciting to hear this is possible but I'm doing something wrong. When I publish at the following settings the background image does not scale it just stays anchored in the upper left corner.
You also can make a background image out of components with say 4 corners, 2 sides and top and bottom infills. It is the infills that will need to be much wider than your screen as to cater for wider/taller resolutions. All anchored into their correct places.
Harry posted a good example of this recently and explained that you can use the "tab" button to isolate and display each component to give you an idea how it is done.
I will try to find that post about the corners and infills since that may work for what I would like to do. What search phrase would you suggest to find it?\