I have a modal demo here (fiddle)...
When it comes up, the background image for the modal window shows up. However, in this code below, you'll see I have a background image for the close window function. It's not showing up and I don't understand why. The CSS should have it showing in the top, right-hand corner.
.reveal-modal .close-reveal-modal {
background: #eee url(http://webfro.gs/south/kb2/images/broken_link.png) no-repeat;
position: absolute;
top: 50px;
right: 100px;
text-shadow: 0 -1px 1px rbga(0,0,0,.6);
cursor: pointer;
}