While sorting through my documents during the holidays, I have found this instructions to create an .ico file which can be used to customise icon in Windows.

  1. Start InkScape with a layout of 256px x 256px and transparent background (my template is here).
    • larger size will not do any good as icons are rather small. 100% zoom will give you a good feel as how the icon will become.
    • transparent background to avoid overseeing any white objects.
  2. Draw whatever you like and save the the file as .svg would be sufficient.
  3. Open the .svg file with GIMP and go to File->Export As (Shift+Ctrl+E).
    • I just take the default options (1.25px/pt) when importing.
  4. Change the extension to .ico and choose 32bpp for the highest quality icon file.

Now you just need to right click on the folders/shortcuts to change their icons. For folders on Quick Access, the File Explorer probably has to be restarted for the changes to take effect.