How to change left-hand menu to image-based?

[galahad2]

I'm in the process of rehashing an osCommerce install replacing menu links etc. with customised images to create a unique feel.

 

Although I can do much of this simply by inserting HTML inside the variable definitions within english.php (<img src...>) I can't see a way of replacing the custom product categories with images (the ones that appear within the Categories box in the top left corner). I assume this is possible though? I've replaced the default categories and subcategories with my own headings, but want to ideally replace the plain text links inside the Categories box with some nice buttons...

 

I've had a look through the /admin/categories.php file but this is over 1000 lines long and horrendous to try and work out.

 

I tried using a Javascript-based mod and although this created the menu without any problem, it had the effect of making the centre table on all pages jump down to the bottom of the page- any ideas why it would do that? I checked and the dimensions of the menu are such that it should fit inside the left column without causing any alignment / size problems elsewhere.