As a way to teach myself more about Keyboard Maestro in general—and Custom HTML Prompts in particular—I wrote a little iTunes song info panel. When called, it shows album artwork (or a placeholder for missing artwork), and the song's title, album, and artist. The final result looks like this:
Very nice! I didn’t read the writeup thoroughly, but it looks well-presented.
As a Custom HTML Prompt enthusiast myself, I love what you’ve done. The prompt looks great! And the HTML is clean and simple. Fantastic job! I’m sure if I had created that, I’d have a bunch of unnecessary garbage in there, so I truly appreciate how clean yours is.
It's working fine for me in iTunes 22.214.171.124 in Mojave. I wouldn't recommend keeping the album art file in the iTunes folder, though. I have mine pointing to the system-defined temporary folder, so it gets wiped regularly:
set albumFile to (":Volumes:" & ( path totemporary items folder from user domain as string ) & "KMiTunesCover" & albumExt)