I have a custom icon on my navigation bar and even when i set the size to 600 x 400 it still shows to small on the bar.
My code for it is :
-(void)goBackOne {
    [self.navigationController popToRootViewControllerAnimated:YES];
}
- (void)viewDidLoad
{
    UIButton *backbtn = [UIButton buttonWithType:UIButtonTypeCustom];
    backbtn.frame = CGRectMake(0, 0, 35, 25);
    [backbtn setBackgroundImage:[UIImage imageNamed:@"done_button.png"] forState:UIControlStateNormal];
    [backbtn addTarget:self action:@selector(goBackOne) forControlEvents:UIControlEventTouchUpInside];
    self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:backbtn];//set new button
    self.navigationItem.hidesBackButton = YES;//hide original back button
}