Adding an overflow image to the main page

I am looking to add an overflow image to the main page and the main page only. Once someone clicks on any other page I want the overflow image to go away.

I am able to add an overflow image that appears on every page by modifying the navSuppWrapper tag and modifying the tpl_footer.php file to include a custom tag and the image file.

Any ideas on how to add an overflow image to just the main page?