MP3tag works on the basis of an album. So you could assign a picture to all files of an album.
For a selection of tracks from multiple albums, the answer is
In short: no
You would have to use a 3rd party tool like
MP3tag works on the basis of an album. So you could assign a picture to all files of an album.
For a selection of tracks from multiple albums, the answer is
In short: no
You would have to use a 3rd party tool like