Section Images not displaying

I have a volunteer graphic designer who created images for two new exhibits and their related sections. The exhibit images displayed but the section buttons are blank. Here are links to the problem pages:
http://plainsart.org/learnonline/exhibits/show/tactile-art
http://plainsart.org/learnonline/exhibits/show/expressions-of-home

I don't see any styles in your CSS that look like they're meant to make any images display for those links.

There are styles that seem to be designed to do that, but they look like they'd only apply to other exhibits.

There should be pics of artwork with the names of the artists attached, such as Star Wallowing Bull, Barry Kleider, Sue Morrissey, etc for the Expressions of Home exhibit, 3 more for the Tactile. Is there something I can tell my volunteer to do on the CSS end that will make the "styles" apply to the correct exhibits? I'm sorry, but I have no expertise, we lost our tech guy during the recession, and my volunteer has never worked in Omeka before.

This really is more of a general CSS question than anything Omeka-specific.

Your current CSS on those exhibit pages has styles like this:

#exhibit-sections #david-bradley a {
    background-image: url(img/artist-section.jpg);
}

Those are for your first exhibit, the one you didn't link to. What you need are new styles like that one, but that refer to the images you're trying to use for your other exhibits, and that refer to the ids used for those links (so something like #mandan-horse instead of #david-bradley).

These styles appear to be located in your exhibit theme's screen.css file.

I have sent this information to my volunteer. Hope she can fix the problem! I'll let you know...