Here's how you can add GNOME Tweak Tool and Unity Tweak Tool to Ubuntu 14.04. These tools will let you customize Ubuntu 14.04.
1. Open a terminal window.
2. Type in the following command then hit Enter.
sudo apt-get install unity-tweak-tool gnome-tweak-tool
Gnome Tweak Tool is well-known powerful tweak tool, With this tool you can manage your Ubuntu environment like: Change theme, icons, fonts, cursor and so on options. Unity Tweak Tool is a configuration tool for the Unity Desktop, providing users access to features and configuration options, and brings them all together in a polished & easy-to-use interface.More at Noobs Lab
Additional Ubuntu Resources