‘Steam Skin Manager‘ contains a tool for applying skins and removing the default skin used by steam. It also comes bundled with 2 skins by default – Ambiance (the dark variant) and Radiance (the bright variant), both the native Ubuntu looks.
* debian package for: Ubuntu, Debian and Linux Mint
* depends on steam:i386 you can obtain here
After installation you will find the ‘Steam Skin Manager’ at your settings-manager, or launch steam-skin in a terminal
Make shure steam isn’t running before changing skin; killall MainThrd