The Numix icon packs provide hundreds of different icons to help you customize your system. Here's how you can install them in Ubuntu 13.10.
1. Open a terminal window.
2. Type in the following commands then hit Enter after each.
sudo apt-add-repository ppa:numix/ppa
sudo apt-get update
sudo apt-get install numix-icon-theme numix-icon-theme-circle
Numix Project is known as they create high quality GTK themes and icons for Linux desktop. This Numix pack contain two icon theme variants: Numix Main, Numix circle, Numix Shine and Numix uTouch. Each variant contains approximately 700+ icons...You can use Unity Tweak Tool, Gnome-tweak-tool or Ubuntu-Tweak to change icons.More at Noobs Labs
Additional resources for Numix Icon Packs