Profile title field as blog title

I have edited the module code to allow the Blog title to be customised using a profile field called "profile_title".

/**
 * Implementation of phptemplate_preprocess_page().
 */
function drupalmu_helper_preprocess_page(&$vars) {
  if($uid = drupalmu_helper_context()) {
  	$user = user_load(array('uid' => $uid));
    $vars['front_page'] = url('blog/'. $uid);
	if($user->profile_title){
    $vars['site_name'] = t('!name', array('!name' => $user->profile_title));
	}
	else {
	$vars['site_name'] = t('!name\'s blog', array('!name' => $user->name));
	}
    $vars['site_slogan'] = '';
    $vars['breadcrumb'] = '';
    // We don't want to display the title twice on the bloggers homepage
    if(arg(0)=="blog") {
      $vars['title'] = '';
    }
  }
}

Next I want to change the title to the user's profile picture.
I tried adding $vars['logo'] $user->picture; but it didn't work.