hi Bill...
I'm wordpress beginner and programming is poor and korean.
I appreciate your effort...and I love your plugin "Display Posts Shortcode"
I'd like to use attatched image(not featured image) as thumbnail image
So I modified your code as bellow...
my result site: http://chang04.wku.ac.kr
source code : http://image.wku.ac.kr/2011/12/display-posts-shortcode-modified.php.txt
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original code: 124 line
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if ( $image_size && has_post_thumbnail() ) $image = ''. get_the_post_thumbnail($post->ID, $image_size).' ';
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modified code: 124 line
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$images = get_children( array( 'post_parent' => $post->ID, 'post_type' => 'attachment', 'post_mime_type' => 'image', 'orderby' => 'menu_order', 'order' => 'ASC', 'numberposts' => 999 ) );
if ( $images ) { $total_images = count( $images );}
$theImage = array_shift( $images );
$image_img_tag = wp_get_attachment_image( $theImage->ID, 'thumbnail' );
if ( $image_size && $image_img_tag ) $image = '<div class="gallery-thumb">'. $image_img_tag.'</div> ';