Paper bats: Draw the outline of a bat on sheets of black construction paper and tack them to the wall with glue dots. I'm gonna plan on making Bend them a bit at the wing to give them a little dimensionality. Best for a room without overhead light.
Silky soft play dough for kids using 2 ingredients: 1 cup conditioner (cheaper the better), 2 cups cornflour/cornstarch, glitter (optional). I was just thinking about affordable gluten-free play dough.