Finder window background colour or image for USB Drive
Only works in icon view &amp; as far as I'm aware only on HFS drives.
I quickly tested with a FAT32 drive which appeared to work, but didn't survive eject/insert]


Open your folder or entire disk &amp; set view to Icon [ Cmd ⌘   1  ]
Show view options [right click or  Cmd ⌘   J  ]
Select Colour or Picture [for picture you then drag &amp; drop an image to the box on the panel.