Prepare the headboard to be painted. Detach the headboard from the bed. Clean it with a commercial wood cleaner following the manufacturer's directions. Lightly sand the surface with fine-grit sandpaper and remove the dust with a tack cloth.
Paint the headboard with a coat of acrylic primer. Use a brush to apply the paint over the wood.
Outline a straight 3-inch border on the headboard. Measure and draw a straight pencil line about 2 inches from the outside edges of the headboard. Measure and draw a second line 3 inches inside of the original line. This provides a defined 3-inch space around the headboard to create a border.
Measure and cut strips of half-round wood trim to fit on top of the lines you have drawn on the headboard. Paint the strips with primer.
Apply white glue to the flat side of the trim and place the wood pieces on top of the pencil lines. Hammer small brads at 6-inch intervals to secure the trim to the headboard. Fill nail holes and seams with wood putty and sand it smooth when the putty has dried. You now have a 3-inch-wide defined border that can be embellished.
Paint the headboard and the added trim with a coat of latex paint. Coordinate the color of paint with your linens for a cohesive look.
Decorate the space between the strips of trim with a hand-painted design. Use an artist's brush and acrylic craft paint to create a border design of your choice.