I found a post regarding putting different background images on different pages, so I tried it, but I'm not getting it to work.
I used Firebug to find out where I would want to change the middle & footer background images as well, but I'm not having any luck, so I don't know if I'm using the correct id for the footer and the main content section.

Here is the code I used:

body.page-id-2 {background-image: url("/wp-content/themes/atahualpa/images/header1.jpg");}
footer.page-id-2 {background-image: url("/wp-content/themes/atahualpa/images/footer1.jpg");}
middle.page-id-2 {background-image: url("/wp-content/themes/atahualpa/images/main_bg1.jpg");}

URL is http://wildwildwesthomes.com/listings/

I also turned off the right sidebar on that page, but what am I missing?

It looks like you don't have the 3.6.7 PATCHES applied Here are the links.

• PATCH 367-01: Odd effects when 'CSS: Compress' = 'Yes'
• PATCH 367-02 is incorporated in BUGFIX 367-04
• PATCH 367-03: PHP errors when adding widget areas in index.php
• PATCH 367-04: Hovering over a Post/Page title only shows "Permanent Link to"
• PATCH 367-05: Site Title appended after the 'WordPress SEO by Yoast' title

apply them before we go any further and re-test

I've applied the patches, but it didn't change anything. I didn't apply the patch for the SEO Plugin however, as I'm not using it.
What should I try next?

body.page-id-2 should work but the other two should probably be

.page-id-2 #middle and .page-id-2 #footer

How did you come up with the code you used?