I think your room looks stunning as it is and putting anything on that wall may take away its calmness and beautiful lines.
However if you really feel you’d like artwork I would suggest you use paper to mock the sizes of the art you’re considering and see how it looks.

I would look for a wallpaper or digital art for the wall behind the bed. Choosing an image or pattern with vertical lines (such as trees) will trick the eye to visually add a little height.

Panoramic - pick a calm photo/ painting that wont take away from the calmness and serenity of the room.

Thats a perfect panoramic photo as the colours match in with the bed which will keep the room peaceful.

On account of your beamed detail and quite low ceiling I would skip artwork over the bed. You have quite a tall headboard with detail and there's too much competition from other items for the art to add anything.

I agree with Isla Cherry that it would probably compete with other items but if you went for something like what Jonathan found I think it would still work. Another option is to hang it on the opposite wall from the bed.

Although it’s a tight spot, I thing a nice panoramic canvas would look great. These two pics are from Etsy.

The bottom one would be best in my opinion if you’re interested in one of those two. It is thinner which would fit in better

I think Jonathan’s panoramic mural would work wonderfully.
I would change the button styled headboard to something lower & lighter in colour and less detailed. Or no headboard instead two low tufted or wedged pillows placed underneath your current pillows?
Make your bed blend I more with the mural colours by using the colour tones throughout your bedding (as below examples show batting the actual large murals).

Perhaps keeping your bedside furniture & lighting to a minimalist style so as not to conflict with the background. Maybe, paint the lightest colour from the mural on the low ceiling and walls? I think there are endless ways to make this space tranquil & calm with a landscape mural such as shown.

Hi Amelie,

Your bedroom looks beautiful! I think adding art would elevate the space.

I would recommend the following two options which are in-keeping with the cosy, calming theme you have designed.

Deep Blue Sea Framed Art

Navy Shore Framed Print Set

Can't wait to see the finished look!