I imagine: an MMO browser game where there are 2-4 teams, around 1000 players in each, and some picture is shown on the screen like "kitty" or "car". The timer counts down to 1, and then the first group to make the picture correctly, wins and gets to brag. That's it.

What would make it possible is: 1. On a player's screen, all other mouse cursors will appear in the background, and lighter or blurred. 2. As soon as the time starts, each user could be given a colour from the image, to give them a hint on where to move their mouse but still there are hundreds of the same colour.. 3. There could be a free-for-all, with or without color. Going by the subreddit you shared, it would be awesome to just see what figures they make..