UINavigationBar and UINavigationItem background image

UINavigationBarItem Background Image

navigationController.parentViewController action:@selector(yourmethod:)];

             self.navigationItem.leftBarButtonItem.image = [UIImage imageNamed:@"leftbar.png"];

UINavigationBar Background Image

 [self.navigationController.navigationBar setBackgroundImage:[UIImage imageNamed:@"header.png"] forBarMetrics:UIBarMetricsDefault];