The icon pack can be installed on an assortment of Linux distros, not just Ubuntu
The Numix Project released yet another upgrade for the Numix-Circle Linux Desktop Icon Theme, bringing support for even more applications.This Numix-Circle theme has been updated and, according to its designer, it uses circle-shaped application icons. This is not one of the biggest icon pack available for the Linux platform with only 650 icons, but it’s certainly one of the most interesting.
The theme contains Folders icons, System Settings icons, Indicator icons, Symbolic icons, and a lot more. The developers are working constantly at improving the collection and are adding new icons with each new version they release, which is almost on a weekly basis.
The installation is pretty simple and makes use of a PPA. All you will have to do in order to install the package is to open a terminal and enter the following commands (you will need to be root for this to work):
sudo apt-add-repository ppa:numix/ppa
sudo apt-get update
sudo apt-get install numix-icon-theme-circle
You will also need GNOME Tweak Tool or some other application to change the icons, but it is totally worth your while. If GNOME Tweak Tool doesn't work (it has some issues with the latest Ubuntu 14.04), you can try Unity Tweak Tool.