Last summer, I painted a tree on the Straight-haired girl's wall. She absolutely loves it and wants to turn her entire room into the Big Woods. For Valentine's Day, I made up little red hearts from construction paper and wrote things I appreciate about her on them. Then, I taped them to the wall over the top of the leaves on the tree. She moved them all to her owls, right over her bed.
Red construction paper - $1.99, sharpie markers - $3.99, fillin' up the love tank - priceless.