Ubuntu Tweak is one of the best Ubuntu desktop customization tool which is used to customize entire desktop and system configuration options which are unavailable via native system tools.
Tualatrix Chou, creator and maintainer of Ubuntu Tweak, Finally announced the project is no longer under maintenance on
May 02, 2016. He updated the same on his own Chinese blog, Ubuntu Tweak launchpad page & Ubuntu Tweak github page too.
Last time he announced the same but Ubuntu users requested him to reconsider this and finally he accepted and worked for further development but now he officially announced and ubuntu-tweak.com website redirected to his blog.
See the below screen shots which are taken from corresponding sites. Officially blog update.
Ubuntu tweak Launchpad page
Alternatively we can use Unity Tweak Tool to customize our Unity desktop.