The standard method for including album art (outside of iTunes world, I don't know what things are like there) has always been folder.jpg or folder.png in the f

The standard method for including album art (outside of iTunes world, I don't know what things are like there) has always been folder.jpg or folder.png in the folder. (And several other common names.) It can be as big as you like. Software should always copy the art, and of course dragging and dropping the album in your file manager makes this happen automatically. It's absurd to spend the same 0.5MB or more on the same piece of art over and over on every tiny lossy-encoded track. Even with FLAC it's pretty questionable. Better to include a tiny 100x100 jpg or nothing at all. I actually recently encountered a bug with a music encoding tool where it failed to resize my album art when creating Opus files. I ended up with an Opus-encoded album that was bigger than the FLAC version because every single song had a 30 MB high res scan of the vinyl album art embedded in it.