Hi!! I don’t make backgrounds but I would check out
Episode Life for tons of backgrounds, overlays, script templates, etc. But be sure to give credit
You can also look at Pixabay and Pexels for stock free images - meaning they do not require any credit
You can also check out Hollywood’s List of Everything for links to various drives - most of these do require credit
These are all free to use! Some just require credit whereas others do not