If you ctrl-click iTunes, “show package contents”, open the file “Info.plist”, you will see all available file types for iTunes. For example, search the file for “mp3” and you will see the “kind” (“MP3 Audio File”), extensions and mime types.
However, as you know, “kinds” are localized strings. So, in my system “MP3 Audio File” is “Archivo de Audio MP3”.
(just a warning, for portability’s sake )
Most probably, you can find more types in the propper app, such as wmp, rm, etc.