Adaptive Toolbar by Thibov16

Adaptive Toolbar is a Firefox extension designed to enhance your browsing experience by dynamically changing the color of the toolbar based on the theme-color property of the current website. Whether you prefer a seamless integration with the website's color scheme or have a custom theme in mind, Adaptive Toolbar gives you the flexibility to tailor your browser's appearance.

There's a restriction in Firefox that prevents this extension from accessing images from other extensions or themes. This means you can't use themes with images.
There is one exception: you can use a custom theme with images made in Firefox Color.