Turn an entire wall into a dramatic headboard with paint and molding purchased from a hardware or home and garden center. Use photos of architectural elements and hand-carved wooden wall panels from books and magazines as inspiration. Mimic the look you like by painting the wall an accent color and attaching painted wooden moldings to the wall with a nail gun. Make sure the moldings are spaced above pillow height and within one foot of the ceiling. You could also hang a large painting on the wall over the bed framed by molding.
Reclaimed barn wood can turn a plain wall into a rustic headboard. Attach it to the wall 2 feet above the bed and pillows. Whitewash the wood for a cottage feel or stain them to match existing wood in the room.
You could also give an old metal garden gate new life by turning it into a wall headboard. You can find vintage metal garden gates at antique or architectural supply stores. Spruce it up with a cleaning and new coat of paint before attaching it to the wall above the bed.
Refurbish an unusable headboard of appropriate size from a garage sale or second-hand furniture store. Clean and strip it of existing finishes and paint. Use interior paint to create a whimsical design. If your painting skills won't allow you to be the next great artist, just use bright paint colors and painter's tape to paint blocks of color. Once the paint is dry, apply a paint sealer. Allow it to dry completely before attaching it to the wall.