m4p and m4a AAC files from iTunes
File Juicer can extract artwork from m4p, m4a and mp3 files. You can also extract a bit of text, just like from ID3
tags in MP3 files, with the added bonus of discovering that your name is in the file too, if you bought the file. To
take a further look into what is in your iTunes Library, you can take a look at Automator which has actions for
controlling iTunes.
Apple recommends that you protect your investment in m4p files by backing up your library.
AAC files are the naked audio without artwork etc. It makes no sense to drop those on File Juicer.
M4A files are AAC files with cover art and other meta tags.
Using iTunes libray with Roon
If you are importing your music from iTunes into Roon and have more than one image per album, you will normally only get one image over. Fortunately Roon can handle extra images if you place them in the same folder as the audio files.