My Dropbox and Viber icons are blank and I don't really know how to fix this. I tried adding the icons to the theme, but nothing happens. I'm running Xubuntu 16.10, but it has been an issue since I installed 16.04.
[Desktop Entry] Version=1.0 Type=Application Name=Viber Comment=Viber VoIP and messenger Icon=/usr/share/pixmaps/viber.png Exec=dbus-launch /opt/viber/Viber NoDisplay=false Categories=Application;Network; StartupNotify=false Terminal=false
to fix the Viber icon.