WPAlchemy - Adding thumbnail to shadowbox gallery

gallery.php

<?php global $mgallery; ?>
                
				<?php $loop = new WP_Query( array( 'post_type' => 'gallery_main', 'posts_per_page' => -1, 'orderby'=> 'date', 'order' => 'DESC'  ) ); ?>
                
                <?php while ($loop->have_posts()) { ?>
                <?php $loop->the_post(); $mgallery->the_meta($post->ID); ?>
                    <div class="mgallery">
                    
						<?php $gallery_images = $mgallery->get_the_value('gallery_image'); ?>
                        
                        	
                        
                        <?php $i = 0; foreach ($gallery_images as $w) { ?>
                            
                            <?php //get the attachment id dynamically to use with wp_get_attachment_id
								 global $wpdb; $attachment_id = $wpdb->get_var("SELECT ID FROM $wpdb->posts WHERE post_parent = '$post->ID' AND post_status = 'inherit' AND post_type='attachment' ORDER BY post_date DESC LIMIT 1"); 
								 $attach = wp_get_attachment_image_src( $attachment_id, 'thumbnail' ); 
								 //$attach[0] => url
								 //$attach[1] => width
								 //$attach[2] => height
								 ?>
                                                
                        	<a rel="shadowbox[<?php $galleryname = get_post_meta($post->ID,'_gallery_name',TRUE); echo $galleryname['galleryname']; ?>]" href="<?php echo $w['imgurl']; ?>" title="<?php echo $w['title']; ?>"><img class="gimage<?php echo (!$i) ? ' first' : '' ; ?>" src="<?php echo $attach[0]; ?>" width="<?php echo $attach[1]; ?>" height="<?php echo $attach[2]; ?>" alt="<?php echo $w['title']; ?>"/></a>
                            
                        <?php $i++; } ?>
                    		<div class="gtitle">
								<a rel="shadowbox[<?php echo $w['gname']; ?>]" href="<?php echo $w['imgurl']; ?>" title="<?php echo $w['title']; ?>"><?php the_title(); ?></a>
                            </div><!-- end gtitle -->                    
                    </div><!-- end mgallery -->
                <?php } ?>