Common subdirectories: sites/all/modules/lightbox2/css and sites/all/modules/lightbox2_improved/css
Common subdirectories: sites/all/modules/lightbox2/images and sites/all/modules/lightbox2_improved/images
Common subdirectories: sites/all/modules/lightbox2/js and sites/all/modules/lightbox2_improved/js
diff -up sites/all/modules/lightbox2/lightbox2.admin.inc sites/all/modules/lightbox2_improved/lightbox2.admin.inc
--- sites/all/modules/lightbox2/lightbox2.admin.inc	2009-01-07 09:46:47.000000000 -0800
+++ sites/all/modules/lightbox2_improved/lightbox2.admin.inc	2010-05-03 15:24:25.000000000 -0700
@@ -52,6 +52,13 @@ function lightbox2_general_settings_form
     '#default_value' => $use_lite,
   );
 
+  // Add checkbox for thumbnails list.
+  $form['layout_fieldset']['lightbox2_use_thumb_list'] = array(
+    '#type' => 'checkbox',
+    '#title' => t('Use thumbnail list'),
+    '#description' => t('Displays a thumbnails list with all the grouped images in the modal window.'),
+    '#default_value' => variable_get('lightbox2_use_thumb_list', FALSE),
+  );
 
   // Add checkbox for alternative layout.
   $form['layout_fieldset']['lightbox2_use_alt_layout'] = array(
diff -up sites/all/modules/lightbox2/lightbox2.module sites/all/modules/lightbox2_improved/lightbox2.module
--- sites/all/modules/lightbox2/lightbox2.module	2009-01-08 04:34:25.000000000 -0800
+++ sites/all/modules/lightbox2_improved/lightbox2.module	2010-05-03 15:24:16.000000000 -0700
@@ -696,6 +696,8 @@ function lightbox2_add_files() {
     'iframe_border' => variable_get('lightbox2_frame_border', 1),
     // Video settings.
     'enable_video' => $enable_video,
+    // Thumnails list settings.
+    'use_thumb_list' => variable_get('lightbox2_use_thumb_list', FALSE),
   );
   if ($enable_video) {
     $js_settings['flvPlayer'] = check_plain(variable_get('lightbox2_flv_player_path', '/flvplayer.swf'));
@@ -733,6 +735,9 @@ function lightbox2_add_files() {
     }
     drupal_add_js($path .'/js/lightbox.js', 'module', $js_location);
 
+    if (variable_get('lightbox2_use_thumb_list', FALSE)) {
+      drupal_add_js($path .'/js/jquery.scrollTo.js', 'module', $js_location);
+    }
   }
   // Lightbox Lite.
   else {
Common subdirectories: sites/all/modules/lightbox2/translations and sites/all/modules/lightbox2_improved/translations