MP3 Album Art

Can anyone recommend a MP3 tagger that will embed album art into my MP3's without touching the already existing tags.

I use MusicBrains Tagger/Picard to tag my MP3's and I don't wanna ruin the existing tags when updating my MP3's with album art.

What would be really nice is if it could be done through a commandline for scripting.

Album art goes in the folder, not the mp3s (that would just be retarded).