Вы можете использовать этот код, я думаю, он будет вам полезен.
UIButton * button = [UIButton buttonWithType: UIButtonTypeCustom];
button.frame = CGRectMake (0,0,50,32);
[кнопка setBackgroundImage: [UIImage imageNamed: @ "btn_back.png"] forState: UIControlStateNormal];
[button addTarget:self action:@selector(BackBtnClicked) forControlEvents:UIControlEventTouchUpInside];
UIView *backButtonView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 50, 32)];
backButtonView.bounds = CGRectOffset(backButtonView.bounds, -1, -4);
[backButtonView addSubview:button];
UIBarButtonItem *barButtonItem = [[UIBarButtonItem alloc] initWithCustomView:backButtonView];
//barButtonItem.imageInsets = UIEdgeInsetsMake(-6, 20, 30, 0);
[self.navigationItem setLeftBarButtonItem:barButtonItem];