Default only works on certain pages/posts:

add_action('genesis_post_content', 'genesis_do_post_image');
/**
* Post Image
*/
function genesis_do_post_image() {
if ( !is_singular() && genesis_get_option('content_archive_thumbnail') ) {
$img = genesis_get_image( array( 'format' => 'html', 'size' => genesis_get_option('image_size'), 'attr' => array( 'class' => 'alignleft post-image' ) ) );
printf( '%s', get_permalink(), the_title_attribute('echo=0'), $img );
}

}

Here’s a sample fix:

remove_action( 'genesis_post_content','genesis_do_post_image');
add_action( 'genesis_before_post_content','tapestry_do_post_image');</code>

function tapestry_do_post_image() {
$img = genesis_get_image( array( 'format' =&gt; 'html', 'size' =&gt; genesis_get_option('image_size'), 'attr' =&gt; array( 'class' =&gt; 'aligncenter post-image' ) ) );
printf( '<a title="%s" href="%s">%s</a>
<div class="clear"></div>
', get_permalink(), the_title_attribute('echo=0'), $img );
}