For years, when editing previously tagged FLAC files, if attached album art seemed very large (say over 750kB), I would remove it and replace with smaller image, perhaps around 50kB (via mp3tag). Imagine my shock when I recently discovered this has no effect on file size (yes, I'm a noob). I'd suppose there is a command line option to set metadata size at time of encoding? Can metadata allotment be managed after the fact, or is re-encoding necessary?
See this thread for a similar conversation.