CSS background image fails to repeat below viewport

CSS background image fails to repeat below viewport

We repeat a textured background on www.tekiki.com, but anything below the
viewport isn't repeated for some reason. The background renders as white.
Here are the CSS rules for our body element, which contains the repeating
image:
font-family: 'Signika', verdana, tahoma, arial, sans-serif;
font-size: 16px;
line-height: 22px;
color: #5c5c5c;
margin: 0;
padding: 0;
border: 0;
background: #cbe9f1 url(/images/web/main_bg.png) repeat top left;
background-attachment: fixed;
How do we get the background image to tile correctly? Thanks!