Beside administrator show only image media files.

show_only_image_media_files.php

<?php

/**
 * Beside administrator show only image media files.
 *
 * @param [type] $query
 * @return void
 */
function show_only_image_media_files( $query ) {

    if ( ! current_user_can('administrator') ) {
        $query['post_mime_type'] = 'image';
    }
    return $query;

}
add_filter( 'ajax_query_attachments_args', 'show_only_image_media_files' );