I made a tiny pixel character creator called Pixabots. It generates 10,752 unique combinations from four categories — eyes, heads, bodies, and tops — all bouncing on a little idle loop.
This pack is a curated 2,000 of them, ready to use. Free.
Not sure where I saw this, there is a live editor at Pixabots — Pixel Character Avatars which is fun. Could be useful in class I think. Perhaps in Scratch when an uploaded gif is turned into a sprite with a costume for each frame.