iphone - Custom Navigation Bar Buttons

Question

I have custom Navigation Bar with metallic style.

It's pretty simple in iOS 5+.

You may change all your Navigation Bars by this code:

UIImage *navBackground =[[UIImage imageNamed:@"navigationBar.png"]    resizableImageWithCapInsets:UIEdgeInsetsMake(0, 0, 0, 0)];
[[UINavigationBar appearance] setBackgroundImage:navBackground forBarMetrics:UIBarMetricsDefault];

But what about buttons? Do I need to make background images for all button sizes to fit navigation bar style? It's gonna be hard if your app localized.

But there are Apple's Apps with custom navigation bars: - Notes; - Reminders;

It seems to me that there is no images for each button for each size. They just somehow make navigation bar color darker to look like buttons.

Any help?