You can add the taxonomy parameter.
function add_image_category_filter() {
$screen = get_current_screen();
if ( 'upload' == $screen->id ) {
$dropdown_options = array(
'taxonomy' => 'YOUR_TAXONOMY',
'show_option_all' => __( 'View all categories', 'iCats' ),
'hide_empty' => true,
'hierarchical' => true,
// default is cat which wouldn't filter custom taxonomies
'value_field' => 'slug',
'name' => 'YOUR_TAXONOMY',
'orderby' => 'name', );
wp_dropdown_categories( $dropdown_options );
}
}
add_action( 'restrict_manage_posts', 'add_image_category_filter' );