If you are creating a theme to upload to wordpress.org you have to provide wordpress menu support but if it is your own theme then that is not a problem. Anyway under Appearances >> Menus you can attach custom links, categories as well as posts and pages so not sure why you want to hardcode this. There are also plugins that allow you to upload images to menus like http://wordpress.org/plugins/menu-image/ or you can do it manually as a background image via css