heres a site i found when looking for was to make a navigation menu with images: sexy css hover buttons
it involves using class and id selectors to name the unordered list and the different instances of the list items inside it so that they can be customized individually, i.e the list item itself, the link inside that list item and then the hover instance of the link (what happens when you hover over the link with the curser)

heres a screenshot of some of the code :D