Remember being younger and writing all over stuff? Benches in the locker room at school, walls in stalls, etc. “Dave loves Michelle 6/8/10”, and drawings of random things.
Remember the Million Dollar Homepage? A limited amount of space for sale at $1 per pixel, 1mm pixels.
Why isn’t there a big graffiti wall on the Internet. Simple tools of a paintbrush that can be fine size to thicker. Select color. You could draw anywhere on the “wall”. The wall starts small until it starts filling up. Then sections open up. Maybe when you get enough friends to draw, your drawing becomes permanent? Or maybe they all are permanent. Maybe you can have your own wall section that your friends add too, as they add then more wall opens up for their friends to contribute too.
UPDATE: google search for “infinite canvas”.