I went to a museum exhibit with this concept once. Huge room with projectors showing a seascape on the walls. There was paper for kids to draw fish and other things on and then scan. The system would then drop the digital fish in to the scene with hundreds of other kid drawn fish. The fun was trying to find your fish.

Found it!
https://futurepark.teamlab.art/en/playinstallations/sketch_aquarium_connected_world/