I don't know what style you're thinking of but here's a link with ideas to get you started:
Here's a tutorial for a tufted one that might help: https://www.heytherehome.com/diy-upholstered-headboard/
Hi Kat, there are lots of ideas here:
Hi Kat. I'm Cindy. My husband and I want to make a headboard from an old door. We want to turn it on its side and attach a mantle down the entire length. We will finish the sides with trim. We will paint the entire thing with an off white color that we have from a different project. We will attach it above our bed and anchor it using the studs inside the wall.
Paint or outline a shape on the wall it is against, or Buy a second hand headboard from a charity shop or on ebay etc. or cut or have cut for you a piece of mdf in the shape you desire. Add two pieces of timber to the headboard once finished to be able to slip over the screw fixings at the head of the bead and also to be screwed onto the headboard. (Oblong with a slot at the end to go over the screw fixings.) Best wishes.
I made one by cutting up a 4x4 into blocks and staining them. You can see how I did it here: https://www.flippingtheflip.com/2015/03/how-to-diy-wood-block-headboard.html