in general this seems to be the accepted methodology of creating a BG image and stretching it.
I have tried this, and although it works if I refresh the screen, which is great, because hopefully people aren't resizing browsers all over the place, when I reduce my screen size, it appears that the height of the image doesn't change. In fact the width only changes for a short while and then stops.
This means if you open the browser full screen, then reduce the browser there is a big white square at the bottom. I built the initial with foundation zurb if that helps anyone to help me.
Can anyone think of why this may be happening?