Watch this:
https://vimeo.com/157394599Each file has an individual image file that is used to generate a thumbnail, when the file itself is viewed in a list. This is the individual file's thumbnail. The [Image File] field in MC points to where this file is located on disk. It can be either embedded in the file's tags (for file types where MC can read embedded artwork), or point to an image file on disk somewhere.
By default, when a
category is viewed in MC (grouped by Artist or Genre, for example) and all of the files contained within a category contain the same image, then the thumbnail is displayed normally (refer to Chvurches in my screencast above). If all of them
do not contain the same Image, then it displays a rotating "fanned stack" of the images. If you point at them and pause, they rotate (illustrated with all of the other artists in the screencast).
If you want to add images and override the normal behavior when showing a group of Artists, then you add a folder called
Artists to your current Cover Art directory. You can check which directory is assigned, and change it if you want, in
Tools > Options > File Locations. Then, if you add a file to that folder whose filename matches an [Artist] field value, MC will show that file instead of the fanned stack when showing a grouping of those files.
If that doesn't explain, then try to ask a little more clearly (overexplain) because I'm not getting it.