There has never been a </img> tag: elements that in DTD days (HTML 2–4) had EMPTY content model, and which these days are called void elements, cannot have an end tag. If you write </img>, it’s a parse error, though in practice all implementations you care about will ignore it.

I'm kind of happy though that <marquee> still works. It's deprecated for a reason, but reminds me of when the web somewhat tried to have a language of common elements rather than being just a sandbox of styles.