I've got an issue with some code, and not sure how to figure it out.

What I have is a functioning base site in the root directory. It has all the functioning code and graphics.

What I want is to be able to have Addon Domains that point to a folder and pull the graphics and code from the main site.

So I've got the index, content, and images all in public_html for the main site.

Then I do the addon domain, and I want it to pull the images and content from the root directory.

www.mainsite.com holds all the files.
www.lookalike.com pulls all files from the root directory - mainsite.com

It works just fine for the content using includes:
- this pulls all the header files, all content pages load without issue. However, when the header.php file, attempts to load the images
They do not load.

I've tried ../, ./, ../../, /../../, and a million other variations, but it just does not work no matter what I try, but all pages and content files load just fine, and they are pulling from the content folder just one directory above them.

Is this clear as mud? Did I make any sense?