Index: wp-content/themes/twentytwelve/content-page.php
===================================================================
--- wp-content/themes/twentytwelve/content-page.php	(revision 23179)
+++ wp-content/themes/twentytwelve/content-page.php	(working copy)
@@ -10,6 +10,7 @@
 
 	<article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
 		<header class="entry-header">
+			<?php the_post_thumbnail(); ?>
 			<h1 class="entry-title"><?php the_title(); ?></h1>
 		</header>