In the below screenshot I use “AwOken” icon set (its name is really written like that, not a typo).
To install a icon theme, either install via PPAs or copy (the extracted) icon folder directly to /usr/share/icons or ~/.icons
Adding a PPA is often frowned upon, but since I really like it, I am willing to take the risk!
You need to install software-properties-common to be able to add PPA using command line, to install it:
sudo apt-get install software-properties-common
I have installed AwOken icon theme following the guide here:
sudo add-apt-repository ppa:alecive/antigone
sudo apt-get update
sudo apt-get install awoken-icon-theme
AwOken is a special theme that comes with a script to customize itself, here is the instruction given by the author, skim through it and you will see how awesome it is: Installation and Instructions (PDF)
Or if you want to learn by doing, below is the command to trigger all the options.
Apply the icon theme.
Open Lxappearance to change the icon-theme to AwOken.
Here is how it looks on my system: