function custom_header_image($random_image) {

/* CATEGORY AND PAGE IDS FOR CUSTOM IMAGES */
$custom_image_ids = array(2,8,28,617); // modify at will

/* GET CURRENT CAT OR PAGE INFO */
    // Test if we are inside a cat archive, a post, or a page
if ( is_category() || is_single() || is_page() ){

/* CHECK IF POST HAS FEATURED IMAGE */
if (is_single() || is_page() ) {
global $post;
$post_id = $post->ID;
$featured_array = wp_get_attachment_image_src( get_post_thumbnail_id($post_id), 'full');
$featured_image = $featured_array[0];

// Check if this is a post
if ( is_single() ) {
// Retrieve post info
$curr_post_id = $post_id;
$current_args = array('orderby' => 'ID', 'order' => 'DESC');
$current_array = wp_get_post_terms( $curr_post_id, 'category', $current_args );
$current_id = $current_array[0]->cat_ID;
$current_slug = $current_array[0]->slug;
$parent_id = $current_array[0]->parent;
// Test if current post cat has parent cat
if ( $parent_id ) {
$parent_array = get_term($parent_id,'category');
$parent_slug = $parent_array->slug;
$ancestor_id = $parent_array->parent;
// Test if current post cat has ancestor cat
if ( $ancestor_id ) {
$ancestor_array = get_term($ancestor_id,'category');
$ancestor_slug = $ancestor_array->slug;
}
}
// If it is not a post, it's a page
} else {
// Retrieve page info
$curr_post_id = $post->ID;
$current_array = get_page( $curr_post_id );
$current_id = $curr_post_id;
$current_slug = $post->post_name;
$current_ancestors = get_ancestors ($current_id, 'page');
$parent_id = $current_ancestors[0];
// Test if current page has a parent
if ( $parent_id ) {
$parent_array = get_page( $parent_id );
$parent_slug = $parent_array->post_name;
$ancestor_id = $current_ancestors[1];
// Test if current page has an ancestor
if ( $ancestor_id ) {
$ancestor_array = get_page( $ancestor_id );
$ancestor_slug = $ancestor_array->post_name;
}
}
}
// If it's neither a post nor a page, it's a category
} else {
// Define unneeded $post_id value as false
$post_id = false;
// Retrieve cat info
$current_id = get_query_var( 'cat' );
$current_array = get_term($current_id,'category');
$current_slug = $current_array->slug;
$parent_id = $current_array->parent;
if ( $parent_id ) {
$parent_array = get_term($parent_id,'category');
$parent_slug = $parent_array->slug;
$ancestor_id = $parent_array->parent;
if ( $ancestor_id ) {
$ancestor_array = get_term($ancestor_id,'category');
$ancestor_slug = $ancestor_array->slug;
}
}
}

if ( $featured_image ) {
$random_image = $featured_image;
} else {

/* GET CUSTOM IMAGES FOR CATS */
// Check if we are dealing with one of the selected categories
if ( in_array( $current_id, $custom_image_ids ) || in_array( $parent_id, $custom_image_ids )|| in_array( $ancestor_id, $custom_image_ids ) ) {
// If we are, put together the absolute path
$current_slug_slash = $current_slug . '/';
$parent_slug_slash = $parent_slug . '/';
$ancestor_slug_slash = $ancestor_slug . '/';
$image_start_path = get_stylesheet_directory() . '/images/custom-headers/';
$image_start_dir = get_stylesheet_directory_uri() . '/images/custom-headers/';
$custom_images = '';
// Check which directory to retrieve the custom images from and save them in a variable
if ( $ancestor_slug ) {
$image_abs_path = $image_start_path . $ancestor_slug_slash . $parent_slug_slash . $current_slug_slash;
if ( is_dir( $image_abs_path ) && $custom_images = glob( $image_abs_path . "/*.jpg" ) ) {
$image_dir = $image_start_dir . $ancestor_slug_slash . $parent_slug_slash . $current_slug_slash;
} else {
$image_abs_path = $image_start_path . $ancestor_slug_slash;
$image_dir = $image_start_dir . $ancestor_slug_slash;
$custom_images = glob( $image_abs_path . "/*.jpg" );
}
}
elseif ( !$ancestor_slug && $parent_slug ) {
                $image_abs_path = $image_start_path . $parent_slug_slash . $current_slug_slash;
if ( is_dir( $image_abs_path ) && $custom_images = glob( $image_abs_path . "/*.jpg" ) ) {

                    $image_dir = $image_start_dir . $parent_slug_slash . $current_slug_slash;
} else {
$image_abs_path = $image_start_path . $parent_slug_slash;
$image_dir = $image_start_dir . $parent_slug_slash;
$custom_images = glob( $image_abs_path . "/*.jpg" );
}
}
            elseif ( $current_slug && !$parent_slug ) {
                $image_abs_path = $image_start_path . $current_slug_slash;
                if ( is_dir( $image_abs_path ) && $custom_images = glob( $image_abs_path . "/*.jpg" ) ) {
                    $image_dir = $image_start_dir . $current_slug_slash;
                }
            }
            // Retrieve random images from custom image  obtained
if ( $custom_images ) {
$key = array_rand( $custom_images );
$random_image = $image_dir . basename( $custom_images[$key] );
}
}
}
}
// Return the random image obtained
return $random_image;
}
add_filter( 'graphene_header_image', 'custom_header_image' );

/***********************************************************************************************
    SCRIPT END
***********************************************************************************************/
?>