Okay, let me try and make this a little more clear.

I've got the main directory, and then within the main directory I've got a folder. In that folder is the index.php file which pulls all content and images from a folder a directory above it.

If I go to the site via: www.mainsite.com/ADDON everything works fine. But if I go to the site via: www.ADDON.com images don't load, but content does.