Random avatar generator?

Instead of having the user upload an avatar what if they could instead use DiceBear to add an avatar? The site would not be filled with uploaded avatars if the user does not have a Gravatar. I am looking into how I should handle 40 students who need an avatar in their profile screen.

EDIT.
How would I go ahead and decorate the default grey circle and letter avatar with CSS used in Fluent Community?