The windows do provide light, so you would lose some natural light if you covered them up with anything. And I do think it would look odd if you left the windows like that with a headboard that partially covered them. If you do use a taller headboard, treat the windows as large windows and install floor to ceiling drapes so that the windows look large. Possibly even use drapes on the full wall.

I would stick with a headboard below window height, with artwork above.

Any interest in an arched design? Might help if you showed a picture of what you do like.

If possible, use your bed without any head board until you can find one that doesn't cover the windows. Choose one that is as uncomplicated as possible -- even consider metal ones. Take some measurements. Is 40" too tall?

https://www.amazon.com/Linenspa-Decorative-Black-Metal-Construction-Vertical-Bar-Inches-Tall/dp/B08GL11P94/ref=sr_1_15?dchild=1&keywords=king+size+metal+headboard&qid=1626127536&sr=8-15

Here is a picture of one of the beds I like. Height is 70". From my floor to the bottom of the window is 59".

I'd stay below the window with the headboard, unless you used an iron open design. Is that the only wall option for the headboard in the room? The arched headboard was a good idea so you get some height while still keeping the windows clear.

Agree with kpkowski you need furniture that is in proportion with the room. What are the room's dimensions? That bed looks heavy for the room size

Here are a few bedroom designs from designers we follow. Take note of the beds/headboards used.

Valley View Rd · More Info

Chloes Bloom New Build · More Info

South Pasadena Master Bedroom · More Info

Palma Plaza · More Info