Custom Folder Icon for Bookmark Toolbar in Firefox, Iceweasel, PaleMoon...

What if your Mozilla-browser's favourite theme lacks nice folder icons?
You don't have to rewrite the theme, it's enough to create or edit your
profile-folder/chrome/userChrome.css e.g. like this:

@namespace url(; /************************ DO NOT remove the Above line **********************/ .bookmark-item[container="true"] { list-style-image: url("file://<full-path-to-22px-png-image>") !important; -moz-image-region: rect(0px 22px 22px 0px) !important; }

Remember that the folder path still starts with a slash '/', so you end up having three slashes: 'file:///home/...'

...and of course restart your browser.