I've been using EasyTAG to add a photo to a mp3 file (album cover, really). However, for these files' logos in Nautilus, it only shows the default "mp3" icon, versus my other music, whose file icons are their album cover:
This is also shown in Amarok, which shows the group of songs' album cover, but not the picture for the song itself:
(album in lower left, song in center). Also, the files are purchased from the band's website, versus iTunes or Google Play, so that might be relevant. Thanks!
The problem is the cache. Nautilus creates a cache for image thumbnails at ~/.cache/thumbnails/. There are a number of subdirectories in that location.
It appears that it doesn't automatically refresh the cache if the image changes or as in the case of your question there is a new image to a file. You can verify this by copying your files to a new location and you'll find that Nautilus will display the image at the new album cover of the song in the new location, but not the old location.
Just quickly copy a file or a folder to the desktop and you'll see your image displayed properly.
There might be a different way of refreshing the cache, but one way is to remove it with:
$ rm -r ~/.cache/thumbnails/
Then every time you visit a folder with your song Nautilus will scan the songs and cache the images. They will then display properly.
