You can also just download any GIF and convert it into WebP using an online converter like this. Then you can set that converted WebP as your profile picture.
It's not from a specific place. It was an old GIF I knew and I searched for it. You could search "[something] perfect loop gif" or similar in a search engine.
Ha... I use Voyager and had -no clue- that Lemmy supported either one of these features (previously wef wef). Maybe turn it off in your client, or use Voyager?