Where are the iCloud Drive Libraries icons located? Some apps, like Preview, Pages, or Keynote have folders with different default preview icons publicly visible in the iCloud Drive folder. Where are those icons stored?
Ok, I found it. iCloud daemon (bird) stores info of all the iCloud containers in:

~/Library/Application Support/CloudDocs/session/containers


The info is stored in a plist file with the name of the container for example:

iCloud.com.pvieito.Example.plist


And the icons are stored in a folder with the name of the container:

iCloud.com.pvieito.Example/40x40_iOS.png
iCloud.com.pvieito.Example/80x80_iOS.png
iCloud.com.pvieito.Example/120x120_iOS.png