ArtNet is an icon theme that contains a complete set of icons for GNOME. All icons with high resolution 256x256 px are in SVG vector format. This theme is designed for use with a dark theme GTK. Looks great and well designed icons.

action - 445 icons
animation - 68 icons
apps - 567 icons
categories - 113 icons
devices - 177 icons
mimes - 404 icons
places - 144 icons
status - 334 icons

You can use Unity Tweak Tool, Gnome-tweak-tool or Ubuntu-Tweak to change icons.

To install ArtNet icons in Ubuntu 13.04/12.10/12.04/Linux Mint 15/14/13 open Terminal (Press Ctrl+Alt+T) and copy the following commands in the Terminal:

Terminal Commands:
sudo add-apt-repository ppa:noobslab/icons
sudo apt-get update
sudo apt-get install artnet-icons To install ArtNet icons in Previous Ubuntu/Linux Mint version open Terminal (Press Ctrl+Alt+T