Hello @hunterlipp, I hope you are doing fine.
First, you need to make sure you are modifying the right script, so you need to locate the .site-footer in the theme.css file. After that, you will need to change the background property by adding also the image word, as follow:
Hello @hunterlipp, I am sorry to hear It didn't work...
What if you upload the picture as a file on your store and then change the URL for the one the file will have once is updated on the store?
If so, you will have to use the same backgroud-image property but instead of adding the assets filter, you can directly past the URL?
background-image: URL("your file store URL");
Let me know how it goes!
Sara from The Support Heroes.