I didn't paint the entire back because I wanted to cover it with a graphic (saved lots of paint by leaving that bare spot, didn't I?). The pieces laying on the roof (white wood square) are two side roof supports with holes drilled for dowels that go across the top (under the roof) and can be used to hang ornaments, decorations, etc.
I used "YES" glue (yes it is old and brown but still works fine). I spread it with an old credit card.
I used a brayer to smooth the card down to the back of the stall. (All the mess you see below the project is miniatures displayed under the glass that covers an antique door which is my workbench)
Here is the stall with the backdrop in place. Next time I will show how to make a skirt to go across the back under the lowest shelf.
Thanks for looking!