There are plenty of cool icon sets available for Linux, But "Square" icon set which is new and just released few days back is new competitor of good looking icons. It is elegant, well polished and looks great with all kind of themes but with Unity you must use dark panel theme because its status icons are kind of white/gray. This icon set is compatible with Gnome/other desktops as well as KDE and it has more than 15,000 icons. If you found any missing icon in this set then report to creator. Zorin OS 8 theme used in screenshots. You can use Unity Tweak Tool, Gnome-tweak-tool or Ubuntu-Tweak to change icons.
To install Square icons on Ubuntu 14.04/13.10/12.10/12.04/Linux Mint 16/14/13 open Terminal (Press Ctrl+Alt+T) and copy the following commands in the Terminal:
To install Square icons in Ubuntu 13.04/Linux Mint 15/Any Ubuntu version open Terminal (Press Ctrl+Alt+T) and copy the following commands in the Terminal: