~$ sudo add-apt-repository ppa:murrine-daily/ppa
~$ sudo apt-get update
~$ sudo apt-get install light-themes
Once installed, restart Ubuntu so the new murrine engine gets loaded. Head over to System->Preferences->Appearance and select either Ambiance beta or Ambiance dark beta.
Update: The beta Radiance theme is now available and Ambiance Dark is no longer listed among the themes.
|Ambiance Maverick beta on Lucid desktop|