Custom backgrounds not showing

There are custom backgrounds on almost all the pages of this site. But most of them are not showing. They were showing perfectly, but now they have disappeared.

Here's a page where the custom background shows correctly: http://www.terrybisson.com/this-month-in-history/

But this one is not showing.

http://www.terrybisson.com/life-works/

The screenshot shows that the background is still showing in edit mode

Am I doing something wrong?

Thanks!