Header Category Image

$slug="";
if ( is_category() ) {
    /* category.php or archive.php */
    global $cat;
    $curr_cat = get_category($cat);
    $slug = $curr_cat->slug;
} elseif ( is_single() ) {
    /* It is a post get the first category header */
    global $post;
    $categories = get_the_category($post->ID);
    if($categories) {
        $slug = $categories[0]->slug;
    }
}
if ($slug) {
    //load header image
    if(file_exists( STYLESHEETPATH .'/images/headers/' .$slug .'.png') ) {
        $imguri = get_stylesheet_directory_uri() .'/images/headers/' .$slug .'.png';
        ?>
        <!-- Here is where the header image html would be -->
        <?php
    }
}