Even refreshing the File Explorer multiple times is of no help and the black square appears to be a perpetual issue. Black background behind File or Folder icons on Windows desktop ...

Apple makes it easy to change icons for files and folders on Mac. Here's how it works, along with tips on using images or changing the folder icon color.

If the macOS desktop is looking a little boring, or is in need of a little more personalization than a change of background image, one solution could be to change how files, folders, and apps look.

By installing Attachment Icons for Gmail, you'll be able to quickly identify if it's a PDF, MP3, ZIP, or any other common file type attached to your e-mail without even having to open it.