Funny story, I installed the Ubuntu Kylin theme as discussed here and when I decided I didn't like the "Ubuntu Kylin" theme (mostly because I didn't like the new boot screen & greeter), I removed it...
But now the icons are buggered-up.
Here's what I did to remove the Ubuntu Kylin theme, and also to try to fix the issue (using information I found on Ask Ubuntu)...
sudo apt-get autoremove ubuntukylin-theme
sudo apt-get autoremove --purge light-themes
sudo apt-get install light-themes
sudo apt-get install ubuntu-desktop
sudo apt-get update && sudo apt-get upgrade
Following all this, I restarted the computer, which clearly did not fix the issue.
Obviously it's a theming issue, but what package do I need to re-install and/or how do I actually re-apply the default Ubuntu 16.04 theme?
Unity-Tweak-Tool
to reset the icons. It's even mentioned in the original link you posted. Alternatively, there'sgsettings
way , which is also mentioned by luchonacho's link