An SVG is all you need

Author here: I've just made a ninja edit of the post as it didn't really make clear a quite important point - the SVG is literally 20 years old, and still works, astonishingly. I'm not sure much else I wrote around the time would still work without some editing!

The reverse is kind of true: In the beginning, SVGs were not really an option since it lacked adoption across all major browsers, or more specifically its integration was very heterogenous.

So a SVG you authored 20 years ago for some browser will likely work everywhere today.

Except in an email. Because email is pain.