Use setBackgroundImage to to add a background image to uinavigationcontroller.

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

UINavigationController hide navigation bar

You can also make a custom UINavigationController UIToolbar and set the Background Image to it as given belowâ?¦

#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>

@interface MyToolbar : UIToolbar {}

- (void)drawRect:(CGRect)rect;

@end

//and in .m file

#import "MyToolbar.h"

@implementation MyToolbar

- (void)drawRect:(CGRect)rect {
    backgroundImage = [UIImage imageNamed:@"my-awesome-toolbar-image.png"];
    [backgroundImage drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
}

@end