Ideals to repurpose an unused solid wood king size headboard.
+2
Suggested Project Book
https://www.myrepurposedlife.com/kingsize-headboard-bench/
This will give you a lot of things to think about, from signs to benches, etc. I hope it helps.
https://www.google.com/search?q=repurpose+a+solid+wood+king+size+headboard&rlz=1C1BLWB_enUS700US700&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj0i4vwntzWAhVFRiYKHRG9CfUQ_AUICygC&biw=1138&bih=794&dpr=1.13
Would make a fantastic start to a bench or patio swing
You could use it as a back to a bench.
make a hallway bench, bookcase, put it on a smaller size bed and add shelves for headboard storage.
http://www.bigdiyideas.com/new-upcycled-diy-ideas-old-headboards/