Dimensions - What size, colour, material, will the headboard need to be to work with your bed and surrounding furnishings and colour scheme? When in position is it going to be high enough to see the design and detail on the headboard with 4 pillows?
Light fittings switches and low windows - When choosing the headboard make sure it will fit between lights mounted on the wall, and not cover up any plug sockets or switches. Also another issue are low windows in dormer houses' these can be a challenge as well.
Wall mounted or standard fixings - 90% of the time headboards are fitted to the divan base using the struts/legs provided with the headboard. This only changes when you start going to 5ft king size and above, and at a height of 80cm or above, they then become top heavy and unstable for the base, this also depends on whether your bed base has 1 or 2 fixings per strut/leg.
Wall mounting the headboard is then the alternative.
Not sure whether you want to buy a headboard or a divan or bed frame take a look at our bed frames at Bedframes UK