Code to show all categories on a particular category page?

[davemehta]

We have a category that has a few sub-categories in it and of course when you load the page you see the sub-category images and can then click them to go into the sub-categories.

What I want to do is list all the other top-level categories and show the icons much like when you call /index.php?main_page=index&cPath=0.

A picture tells the story of what I want to do a little easier so i've attached an example image.

Now, I see that in the includes/modules/category_row.php file that the $categories variable lists the sub-categories right there. But problem... I can't define it to give me all the top-level categories. So I found the zen_get_categories() function. But it doesn't return the image for the category so I can't use that to build the full category list like I want. How can I find out the image links so I can show them and make it look like my example mock-up? Oh, and just to note I am using the ImageHandler2 mod so I'd need to find the url of the image that it resized (in the bmz_cache folder).