Easy way to bulk change folder icons in Mac In order to change the icon of one MAC folder, all we need to do is:


Open the image
Copy the image from the menu ("Edit" -> "Copy") 
Right Click on the folder and click "Get Info" 
Click the icon at the top-left
"Edit" -> "Paste" from the menu


At this point I want to bulk change the icons for all my (sub)folders (let's say in one specific master folder).  How is that possible ideally with a script or an existing software? Some extra notes and questions below:


Please note that the images are saved in the subfolders and they are
unique.
In Windows you can simply change the hidden file of each folder called desktop.ini Can we use an .ico file for that? That would come handy in case there are images in the folder (jpeg and png) and only one icon (ico)
With the upcoming push to sign and notarize applications, there is some great technical information on how to use the Icon folder and data fork as the equivalent to the desktop.ini idiom. 


https://eclecticlight.co/2019/07/20/how-to-add-a-custom-icon-to-an-app-without-breaking-its-signature/