One of these I really like that has been around forever is https://robohash.org/ You can generate different variations of robots, cats, and humans.

The source is available as well, and it's also a python module, which is great if you're writing python apps. I found it rather simple to integrate inside of just about any flask/fastapi/django application.

https://github.com/e1ven/Robohash

I use robohash in my hacker news client's user profile page as well as the leaders page:

https://apps.apple.com/us/app/id1464477788

https://play.google.com/store/apps/details?id=com.pranapps.h...

Example:

https://play-lh.googleusercontent.com/RYxCwU-dV9hdzmewDKYmlU...

Those are the exact same cats! Seems like a strict superset, thanks a lot for the link.