Turns out Org mode supports image links natively and we don't have to go out of
spec!
From https://orgmode.org/manual/Images-in-HTML-export.html:
[...] if the description part of the Org link is itself another link, such as
‘file:’ or ‘http:’ URL pointing to an image, the HTML export back-end in-lines
this image and links to [...]
d85768891c