Changing height of view inside UINavigationController

There's no way to change a view controller's view from within the view controller, but you could use a custom container view controller:

// Create container
UIViewController* container = [[UIViewController alloc] init];

// Create your view controller
UIViewController* myVc = [[MyViewController alloc] init];

// Add it as a child view controller
[container addChildViewController:myVc];
[container.view addSubview:myVc.view];
myVc.view.autoresizingMask = UIViewAutoresizingMaskFlexibleWidth | UIViewAutoresizingMaskFlexibleHeight;
myVc.view.frame = CGRectMake(0, 0, container.view.bounds.size.width, container.view.bounds.size.height-200);

// Add your banner
UIImageView* imgView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"banner"]];
imgView.autoresizingMask = UIViewAutoresizingMaskFlexibleWidth| UIViewAutoresizingMaskFlexibleTopMargin;
imgView.frame = CGRectMake(0, container.view.bounds.size.height-200, container.view.bounds.size.width, 200);
[myVc.view addSubview:imgView];

Now you can add the container view controller to your navigation controller instead of your one.