Total time to make: 10 minutes. Total happiness: Immeasurable.
Marker or pencil
Tissue paper (like for presents, not for sneezing)
1) Cut down the cardboard box flat. For my box I had to cut it in half, then tape the two parts together to make a big enough square. (not pictured)
2) Draw your symbol/image/words of choice. (not pictured)
3) Cut out your symbol/image/words of choice. (not pictured, sorry! I forgot to take pictures until halfway through!)
4) Tape tissue paper to one side of the cardboard.
5) BONUS: Use black duct tape to cover the cardboard and make the image stand out better
6) Place decoration in a window; tissue paper facing inward. Place a lamp next to the decoration. NOTE: tissue paper is flammable! Keep a distance between the lamp and the decoration! I'm using a compact fluorescent which doesn't get quite as hot as an incandescent bulb AND the lamp is still a good distance from the decoration. Don't set the house on fire!
7) Bask in the glory of your new home decoration!