We've used some glow in the dark paint to perk up our egg box ghosts, but they are fun just as they are...
You will need:
PVA glue (optional)
Glow in the dark paint (optional)
Black permanent marker
String to hang
Cut the individual egg cases from the box.
Paint white. You may need several layers! Mixing PVA glue into the paint will help with coverage.
When dry, add a coat of "glow in the dark" paint, if using.
When all the paint is dry, draw on some ghostly faces.
Use a pencil to poke holes in the top. Thread some string through and hang up.