Using some recommendations from members on this forum, I just completed a master cleanup of my 120K+ library of .MP3 files. Part of that activity involved removing ID3v1.x from the files leaving ID3v2.3 and APEv2 behind.
I tried ID3v2.4 on a few albums and ran across issues whereby some audio players couldn't process some (or all) of the metadata (tag); most notably: iTunes and Windows 7/10 Media Player.
At the time of this reply, my MP3's contain the following metadata; note the image is JPG: 200x200x96dpi. I've been reading that .JPG's between 400x400 - 600x600 is recommended with the "sweet spot" being 448x448 for compatibility with O/S shell integration tools.