设置NavigationController的背景图片

    RootViewController *rootVC = [[ViewController alloc] init];

   NavigationController *navigationVC = [[NavigationController alloc]initWithRootViewController:rootVC];

   [navigationVC.navigationBar setBackgroundImage:[UIImage imageNamed:@"bj1.jpg"]forBarMetrics:UIBarMetricsDefault];

设置NavigationController的背景图片

原文：http://blog.csdn.net/mhtios/article/details/39313167