Paint the ceiling so it shows stars and the night sky. Paint it with the deep blues and purples of the sky. Add clouds with a moon peeking through them. Make the stars glow by sticking glow-in-the-dark stars and planets on the ceiling.
Add texture to the walls to give them a stone look. A faux Venetian plaster treatment is a good option for this.
Paint a mural of giant chess pieces on one of the walls to create a focal wall. This replicates a theme from the first book, "Harry Potter and the Sorcerer's Stone." If the floor is not carpeted, paint the floor with black and white squares to create the chess board.
Decorate the door. Add stained wooden slats with bolts in them to re-create the look of an old castle door. Screw on a board with wooden pegs to hold coats. Tie skeleton keys onto old twine and then tie them onto the pegs so that it looks like they're the keys to open the door.
Place wooden benches along the wall for seating. Look for old benches that resemble the cafeteria benches in the eating hall at Hogwarts.
Set up a canopy bed like Harry's. Choose heavy red, velvet curtains and a bed with tall posts.
Create shadowboxes that feature Harry Potter memorabilia. Fill them with items such as action figures, wands and collectible cards. You can find these at bookstores, specialty stores or online.
Set up a dress dummy with robes and a tie. It should look like your daughter is storing her Hogwarts uniform on this figure. Place the dress dummy in one of the corners.
Hang framed Harry Potter movie posters on a wall. Position a replica of a Harry Potter mirror in the middle to create a visual wall display and vanity area.
Make broomsticks for a quidditch wall display. Create brooms by getting branches from the yard and tying shorter branches around the end to create the broom head. Use twine for this. Hang these on hooks. Paint a ping pong ball gold to replicate the quidditch snitch ball. Hang this on the wall as well.
Find a lamp that looks like a crystal ball for your daughter's bedside table.