I have taken a look at Qute and Qute like theme before – but this is the first time I have looked at Qute for any Firefox after version 3.6 or so (yes, I find the version numbers a little silly myself now). My thoughts aside, Qute4++ is definitely worth trying out if you are using the latest version of the Firefox browser.
The original designer abandoned the them after Firefox 4, but it seems somebody new has picked it up to continue the work on it. Here is a little more about the icon set that inspired the theme:
Qute is a style of icons and a theme for Firefox which uses them. For various reasons, the theme is no longer available for current versions of Firefox. Qute dates back to the early days of Mozilla Firefox, when it was called Phoenix. It was born out of the desire to make the browser look more modern and better integrate with the system. The theme even shipped as the default for a while.
Want to pick it up? You can do so from the Firefox Add-ons website.