We usually see this kind of avatars in math forums! But I don’t know what they are called.
What is the name of such art?
Also, is there any tool for generating these random shapes?
They’re called Identicons, and they are typically generated based on a user’s IP address.
They’re popular around the Internet largely because they’re a default option for avatars in WordPress:
And of course, they’re on Stack Exchange as well!
I did a quick search, and it seems like this site can generate Identicons. Not sure how copyright works and stuff or what else is out there.