Create a pre-filtered version of the Media Library

Thanks to Milo for the pointer. I’m going to have to work on my application, but the main point is this filters the media library as required.

function only_licensed_images($query){

    global $pagenow;

    if( ! in_array( $pagenow, array( 'upload.php', 'admin-ajax.php' ) ) )
        return;

        $query->set( 'attachment_category', 'Licensed Stock Images' );
}
add_action('pre_get_posts','only_licensed_images');