Configurable Background image for Photogrid about hugo-universal-theme HOT 3 OPEN

Since the background image photogrid.jpg is defined in the site's CSS files, I think this could be relevant:

https://blog.fullstackdigital.com/how-to-use-hugo-template-variables-in-scss-files-in-2018-b8a834accce

from hugo-universal-theme.

from #22 @ngehani

This doesn't seem to work for me:
"Need to 1: copy the carousel.html to layouts/partial along with the 2: style.default.css to static/css and this overrides the default theme elements. The partials are the important piece to copy. The img/.... should contain the assets you want to use."

What is the proper way to overwrite background image. I need to give it exact name per branding guide. Its weird that it's located in theme/universal-theme, unless you use it for SEO purposes?

Can you tell me how to place overwrite it?

from hugo-universal-theme.

In custom.css I tried adding:

background: url('../img/mysite.webp') center center repeat;
but that doesn't work.

from hugo-universal-theme.