The easiest headboard solution we know of? A textile panel hung on the wall (either draped on a wall-mounted curtain rod or simply nailed to the wall).
Above: A length of black and white floral fabric serves as a headboard in this English bedroom photographed by Paul Raeside.
Above: Two textile panels in an Australian bedroom by Phorm Interiors.
Above: An indigo textile in a bedroom photographed by Anita Calero.
Above: A Moroccan wedding blanket as headboard; photo by Polly Wreford.
Above: Tarps hang above the beds in lieu of traditional headboards at the Base Camp Hotel in Tahoe, California.
Above: William Abromowitz photo, via Real Simple.