Can’t see background images on live site

Hi. I’ve uploaded a background image, and it displays properly in Preview mode, but when logged out, the background is solid black. No image.
There are options for Background Colour and Login Block Background Colour, which are set to black by default. However, removing the colour from these areas makes no difference. There is still a solid black background and no image.
I do not have Logo, Retina Logo, or Page Preloader images set.

The page I need help with: [log in to see the link]