You didn’t have to edit the icons … you could have just stored the transparent image somewhere and assigned it to the icon as image, just as I showed.
When it comes to hide the labels, I don’t know. It surely can be done by tweaking the Plasma theme but I don’t know anything about that.
Another way is to change the icons’ names in /home/$USER/.local/share/plasma_icons/*AppName*.desktop
These files look like that:
[Desktop Entry] ... Name=AppName
You can change the Name entry to \s which is the <SPACE> character. Just typing the space character or leaving the name blank won’t do the trick.
EDIT: I now see, you use Cinnamon, not KDE, so these tips are useless for you but surely there must be a similar configuration file.