This is still a work in progress, but....I've already lost several pictures, so I decided to go ahead and post the progress so far.
I'm redoing one of the bedrooms in my house to be a beach themed room. I wanted to make a shutter headboard with some old shutters I have. I laid them out and lined the top (even though some are a little shorter). I screwed them to a 2x4 I laid across the shutters horizontally so they remained even.
I then added 2 2x4's (I screwed into the 2x4 that went across the back) to become the legs of the headboard. I'll eventually mount the whole thing to the wall, but so far...so good...not too shabby for three 2x4's. The size will depend on your bed. This one is going with a full size bed, so I just measure the 2x4 I put the shutters on to be the length of the headboard and the shortest shutter begins below the mattress line.