Dragging a file to the inspector's icon field will not use the file's image, but will instead adopt the generic file icon. In this case, the three selected files will adopt the generic ".jpg" icon ...

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.

It has been observed that conflicts with the default program settings in Windows can cause plain white icons to be displayed on your ‘.docx‘ files.As such, you may not see any Microsoft Word icon.

File Icon Preview Thumbnails Not Showing in macOS Finder? ... In the search field in the top-right corner of the Activity Monitor window, type com.apple.quicklook.ThumbnailsAgent and hit Enter.