VRPlace
VRPlace is prefab for VRChat worlds. it's "r/place" for VRChat. It's a video of a 256x256 pixel grid, and any user can edit 1 pixel on the grid every 20 seconds.
VRPlace is quest compatible! It will add <2MB to the world size.
VRPlace depends on UdonSharp: https://github.com/MerlinVR/UdonSharp
WARNING: Unity might take its sweet time when adding this asset to your world. Do yourself a favor: never inspect the prefab directly. Just drag it right into your scene.
This is a work in progress: Currently, the server resets every 24 hours, or after 30 minutes of inactivity (i.e.: the grid will be cleared every 24 hrs). The server should stay up all the time now, which means the canvas is permanent, if nothing goes wrong. If I need to make server updates, however, the canvas will be lost. I still need to fix that. Soon (tm).