--- headerimage.module	2008-07-28 17:30:46.000000000 +0800
+++ headerimagenew.module	2008-08-06 15:37:20.000000000 +0800
@@ -153,7 +153,11 @@ function headerimage_block($op = 'list',
             }
           node_invoke_nodeapi($node, 'alter', $teaser, $page);
 
-          $block['content'] = theme('headerimage_block', $node, $teaser);
+          // create header_image_show_block hook
+          $block = module_invoke_all('headerimage_show_block', $delta, $node, $teaser);
+          if (empty($block)) {
+            $block['content'] = theme('headerimage_block', $node, $teaser);
+          }
         }
         return $block;
       }