Subcategories on main page
Subcategories on the main page are cached so that they don't slow the page down too much. This means that when you change URL rewriting you need to regenerate categories before the new URLs will appear on the front page subcategories.
To change the apperance, edit the HTML between <!-- BEGIN SUBSUB --> and <!-- END SUBSUB --> in your 'main index' and 'show listings in categories' templates. The template variables that can be used in this area are restricted to ones which are cached. If you want to use more, use the $subhtmlfields tweak to cache additional fields.