If you want to keep the image 100% in view and responsive, as there is no content in the header element then you can simply edit the header elements padding, and change the Top and Bottom Padding to % to match the aspect ratio of the original image.
Calculating aspect ratio:
Background Image Height / Background Image Width * 100
In your case thats:
800 / 1600 * 100 = 50%.
So i would set the Top padding and bottom padding to 25% ( or just one of them to 50% )
This will keep it responsive.