(EDIT Sep, 2010: now with updated packages, see below!)
Running Debian Lenny on my Acer Aspire 5572 notebook I wanted a more “up-to-date” look for it’s Gnome desktop. As I recently came across some screenshots of Ubuntu‘s upcoming release “Lucid Lynx” with it’s new GTK theme I decided to give it a try (you have to get used to the buttons being on the left side of the windows, though!
see screenshot below). Of course, the new Ubuntu Mono iconset goes very well with this theme, so I needed that, too.
To make everything work in Lenny, I grabbed all the source packages from Ubuntu’s package repository and then made deb packages for Lenny from them. I also replaced the Ubuntu logo within the two icon packages with Debian’s logo.
The new Ubuntu “light-themes” (Ambiance/Radiance) need the latest murrine engine, which of course isn’t included in Lenny. So, this was the first thing I took care of. This is the only package which is architecture dependent and I can only provide it for i368. If you need murrine engine for amd64, do as follows:

