How to define images in separate CSS whose image paths get updated on build?

[1O]

I want to define background images in a central stylesheet. How can I update the file paths in the CSS on build, so that the match the suffixed file names in the bundles _files directory?
@Fil 's solution works when used in a markdown page. It also works when I store the css declaration as a global string (example const css = "#test {...}") on that page. It does not work, though, when I return the string by calling a function from a central module (perhaps because the HTML is rendered before the dynamic CSS insertion has finished).

How would I provide a CSS style using a static image (for background) without separately defining it on each affected page?

[Fil]

An idea would be to reference the image as an exported file.

[1O]

works like a charm, thank you!