Hi @richardmconley4! 
Here is an example:
https://x.thunkable.com/copy/949b1d385597d50a8dec9747feb84c59
Here is an alternative to your method. First write down the name of each photo that you want to use and put this in a list. The easiest way to manage this list would be to keep it electronic. next
add all photos to the invisible components section.
Then in your block editor, Create a list of items in which each item is the exact name of the picture that you would want to use as a background. The names in this list should match the file name exactly and this is why you write it out using an electronica method and not pencil and paper. And electronica method will allow you to copy and paste ensuring that you get each letter, spacing, and capitalization correct.
I provide the instructions that upon a button click the background should be set to a random item from the list that contains the names all of the background images.
