nativegallery.php

<?php
add_shortcode( 'slider_gallery', function( $atts ) {

    $defaults = array(
        'show_only' => 'slider',
        'img_class' => 'theImage',

    );
    extract( shortcode_atts( $defaults, $atts ) );

    $post_id = get_the_ID(); //use post id so this shortcode can be used on any page!

    $images =& get_children( 'post_parent='.$post_id.'&order=ASC&orderby=menu_order&post_type=attachment&post_mime_type=image' );

    if ( empty( $images ) ) :
    return false;
    else :

        foreach ( $images as $attachment_id => $attachment ):
        $title = $attachment->post_title;
    $imageData = wp_get_attachment_url( $attachment_id );
    preg_match( '/(.*?)('.$show_only.'.+ ?)/i', $imageData, $matches ); //match all files with 'slider' etc: slider_one.jpg or oneslider.jpg
    $media[] = $matches[0];
    $media = array_filter( $media );
    endforeach;
    foreach ( $media as $m ):
    echo '<img class="'.$img_class.'" src="'.$m.'"/>';
    endforeach;
    endif;

    return;

} );