A code sample how to create custom bulk actions on the media screen in WordPress @see http://wordpress.stackexchange.com/questions/91874/how-to-make-custom-bulk-actions-work-on-the-media-upload-page/

custom_bulk_actions_on_upload.php

<?php
/*
 * Since PHP5 there is no need to pass an reference of $this
 *
 * @see http://php.net/manual/en/language.oop5.references.php
 * [...] As of PHP 5, an object variable doesn't contain the object itself as value anymore [...]
 */
add_action( 'load-upload.php', array( $this, 'custom_bulk_action' ) );


// this is a method or a function? if it is a method, don't forget
// the visibility (public, private, protected)
public function custom_bulk_action() {
  /*
	 * if $_REQUEST['detached'] is set, then we got un-attached media. as we want to handle
	 * only attached medias, bail if we got un-attached medias
	 */
	if ( isset( $_REQUEST['detached'] ) )
		return;

	/*
	 * WP_Media_List_Table doesn't know anything about our actions, so it can't tell us what action was triggered
	 * we have to fetch the action from the $_REQUEST array
	 */
	
	//     // get the action
	//     $wp_list_table = _get_list_table('WP_Media_List_Table');
	//     $action = $wp_list_table->current_action();
	
	//     echo "\naction = $action\n</pre>";
	
	//     $allowed_actions = array("export");
	//     if(!in_array($action, $allowed_actions)) return;

	// handle the top bulk action
	$action_request_top = ( isset( $_REQUEST['action'] ) && ! empty( $_REQUEST['action'] ) ) ?
		$_REQUEST['action'] : '';

	// handle the bottom bulk action
	$action_request_bottom = ( isset( $_REQUEST['action2'] ) && ! empty( $_REQUEST['action2'] ) ) ?
		$_REQUEST['action2'] : '';

	// select the preferred action (top or bottom)
	// here we prefer the top action over the bottom action 
	$action = ( ! empty( $action_request_top ) ) ?
		$action_request_top : $action_request_bottom;

	// bail if no action is set or the action is not allowed
	$allowed_actions = array( 'export' );

	if ( empty( $action ) || ! in_array( $action, $allowed_actions ) )
		return;

	// security check
	check_admin_referer('bulk-media');

    /*
     * yes, this is from edit.php. in edit.php we have posts, not media. media can only have the post types attachment or post
     * a few lines before, we bail if the post type is not an attachment. now guess what post type we have to handle? right, attachments.
     */
//     // this is based on wp-admin/edit.php
//     $sendback = remove_query_arg( array('exported', 'untrashed', 'deleted', 'ids'), wp_get_referer() );
//     if ( ! $sendback )
//       $sendback = admin_url( "upload.php?post_type=$post_type" );

//     $pagenum = $wp_list_table->get_pagenum();
//     $sendback = add_query_arg( 'paged', $pagenum, $sendback );

	// build the query, fetch everything from the request
	$query_args = array();

	if ( isset( $_REQUEST['post_mime_type'] ) )
		$query_args['post_mime_type'] = $_REQUEST['post_mime_type'];

	if ( isset( $_REQUEST['paged'] ) )
		$query_args['paged'] = $_REQUEST['paged'];


	switch ( $action ) {

		case 'export':

        // if we set up user permissions/capabilities, the code might look like:
        // if ( !current_user_can($post_type_object->cap->export_post, $post_id) )
        //  wp_die( __('You are not allowed to export this post.') );

			// make sure ids are submitted.  depending on the resource type, this may be 'media' or 'ids'
			// do array functions only on arrays. do not trust submitted data
			$media = ( isset( $_REQUEST['media'] ) ) ?
				(array) $_REQUEST['media'] : array();

			if ( ! empty( $media ) ) {

				$post_ids = array_map( 'intval', $_REQUEST['media'] );

				if ( empty( $post_ids ) )
					return;

			}

			$exported = 0;
			foreach ( $post_ids as $post_id ) {

				if ( ! $this->perform_export( $post_id ) )
					wp_die( __('Error exporting post.') );

				$exported++;
			}

			$query_args['exported'] = $exported;
			// don't do this on GET-requests! The post_ids array could be very long and the request can cause an overflow!
			// save the IDs in a transient (10 or 30 seconds lifetime) or in a session var
			$query_args['ids']      = join( ',', $post_ids );

			break;

		default:
			return;
			break;

    }

    // we build a new query, there is no need to remove anything
    //$sendback = remove_query_arg( array('action', 'action2', 'tags_input', 'post_author', 'comment_status', 'ping_status', '_status',  'post', 'bulk_edit', 'post_view'), $sendback );

    $sendback = add_query_arg( $query_args, admin_url( 'upload.php' ) );

    wp_redirect( $sendback );

    exit();

}

not working with the real data

Since WP 4.7: https://make.wordpress.org/core/2016/10/04/custom-bulk-actions/