It would let you just drop gifs on the desktop too.

IIRC I had (at my first job, at the age of like 12) a bunch of constantly moving mechwarrior gifs on my desktop. Timberwolf and Vulture for sure.

All in order to prove that the browser should be part of the OS and was not at all gratuitous tying to defeat Netscape.

Yes. I wrote some js to have a drawing of a woman blink her eyes with random intervals. Was fun but super distracting.