Install Shadow flat icon theme on Ubuntu 16.04. Shadow icon is one of the best icon themes for Ubuntu 16.04. Shadow icon theme is a flat icon-theme for Unity and Gnome 3.10+. The icons have colourful circular base with long shadow.
Major Update: 60 new icons specially for Ubuntu top bar (panel bar).
Major Update: Circular mimetypes: Mimetypes are now circular, for better coherence.
Beside most popular apps, this iconset also includes some uncommon apps, used by very specific groups like xmgrace, xcrysden.
Install Shadow Icon Theme (Manually)
Shadow icon theme can be installed manually. Simply download the Shadow Icon Theme from developer github page and extract the downloaded theme to /usr/share/icon directory. You can either place the theme manually or run the foll0wing commands to extract and place it in icon directory.
$ cd /usr/share/icons
$ sudo wget https://github.com/rudrab/Shadow/archive/v2.tar.gz
$ sudo tar -xzvf v2.tar.gz
$ sudo rm -Rf v2.tar.gz
Once installed, use the theme via Ubuntu Tweak Tool, Unity Tweak Tool or activate the theme from command line:
$ gsettings set org.gnome.desktop.interface icon-theme "shadow"
Please note that there is some problem in Unity’s Adwaita theme. Hence they have created separate index.theme for unity. Unity users are requested to copy index.theme_unity to index.theme.
Users can still use old mimetype icons (and places icons also) by copying square_* directories to the respective directories.