Step 1: Open the icon pack app

 

Step 2: Go to the wallpaper section, and pick the wallpaper

Step 3: Click on the download symbol → it is saved to your device

Note: if this step fails, take a screenshot of the wallpaper

Step 4: Open Bubble Clouds and switch to Expert mode

Step 5: In the App Launcher group, click on the background image icon (next to the favorite symbol)

Step 6: Choose source: gallery or photos or images saved on your device (this is different for each Android version and manufacturer) then select the background image

Step 7: Bubble Cloud will let you crop part of the image (a square shaped area)

Step 8: You can do the same for the archive cloud background (app drawer + folders)

Example: Kaorin icon pack