I noticed that ID3 has a list of types of images that can be embedded in an audio file:
The TYPE must be one of the following: OTHER, ICON, OTHER_ICON, FRONT_COVER, BACK_COVER, LEAFLET, MEDIA, LEAD_ARTIST, ARTIST, CONDUCTOR, BAND, COMPOSER, LYRICIST, RECORDING_LOCATION, DURING_RECORDING, DURING_PERFORMANCE, VIDEO, BRIGHT_COLORED_FISH, ILLUSTRATION, BAND_LOGO, PUBLISHER_LOGO.
That’s from the help screen of eyeD3, but many web pages mention it without reference to ID3
Most of them have a use I can understand. But why "BRIGHT_COLORED_FISH"? In the cited web search, I found several mentions, including two Reddit posts asking the same question, but no answer. Adding "why" to the search got the same results.
I couldn’t find an appropriate tag.