Merry Christmas!

After enabled the Author Pane module, the user facebook profile picture could not be loaded for those Facebook logged in users. So i override the author-pane-user-picture.tpl.php as follow.

<?php
/**
 * @file
 * Default theme implementation to present an picture configured for the
 * user's account.
 *
 * Available variables:
 * - $picture: Image set by the user or the site's default.
 * - $account: Array of account information. Potentially unsafe. Be sure to
 *   check_plain() before use.
 * - $imagecache_used: TRUE if imagecache was used to size the picture.
 * - $picture_link_profile: $picture with link to the user profile page if
 *   the viewer has permission to view the user's profile page, otherwise FALSE.
 * 
 * Use $picture_link_profile instead of $picture if you want the picture to
 * link to the account profile page.
 */
?>

<?php if (!empty($picture)): ?>
  <div class="picture">
    <?php print $picture; ?>
  </div>
<?php else: ?>
  <div class="picture">
    <?php
      if (module_exists("fbconnect")) {
        $fbuid = _get_user_fbuid($account->uid);
        if (isset($fbuid)) {
          print theme('fbconnect_user_picture_override', array('fbuid' => $fbuid, 'account' => $account, 'size' => variable_get('fbconnect_pic_size', 'square'), ));
        }
      }
    ?>
  </div>
<?php endif; ?>

Done =)

Reference:

• User Details Block with FBConnect Avatar / Picture