Make colored sand art by stirring a chalk stick in a bowl of salt. it changes the color. Stir less for light color and more for dark richer color. (I used to do this with salt and food coloring. but the chalk stick idea is brilliant!
Draw on wax paper with permanent markers, wrap around candle and heat until image is transferred. It would be great to do this for Mother's Day, or Teacher Appreciation Day - have kids draw on wax paper and give her a personalized candle.
Lights integrated into stairs. Late at night, the stairs can be lit (and safe) without ruining your night vision with bright overhead lights. Would also be a great way to really highlight a gorgeous staircase.