how to use custom theme

[pOH7]

Is your feature request related to a problem? Please describe.
is there a way to add custom.css to www/assets/custom.css, and other resource like background.png

[htquanq]

In k8s, please consider to use configmaps to store CSSs and images.
With images you need to base64 encoded it. You can use b64enc function.

Mount those configmaps into the main container and you will have css and image files available.

[htquanq]

but there's a problem, I tried to apply CSS myself but it cannot show up in the UI. So maybe, extra works would be needed.