Connect a computer to a screen, fire up the pixelvloed server and have everyone in your space send it heaps of individual pixels. Will you combine powers and fill the screen with beauty, or will you overwrite your peer's images? This project is very easy to get started with and allows novice coders to make gradual progress while learning to code in either python of javascript.
We just committed a C version of the pixelvloed server to github. It can be easily compiled on a raspberry Pi zero (or similar device) and is fast enough to turn any old CRT display into a multiplayer canvas. If you use the pi2vga board by mincepi you can create a self contained system for just a few euro's/dollars. At the moment the C version does not yet to pixel scaling and does not broadcast its version/ip/port and resolution yet.