Overwrite background for alternative screen configurations

It would be great to have the option to be able to override the background media as well as the foreground template when setting up alternative screen configurations.
We use the green screen option in our BlackMagic ATEM video controller to overlay the words onto live video of the band for our Facebook livestream. So I have a jpg with the relevant colour as the media background to the songs.
When I set up the alternative screen to display on the projector in the building, with full screen white text on black background, I had to create an alternative template with a text box filled black to overwrite the green colour. It would be much nicer to be able to prepare another background, perhaps with a simple border or one of the Pro Plus Motion backgrounds.