When I create a custom back button, I use the following code:
UIBarButtonItem *leftButton = [[UIBarButtonItem alloc]initWithTitle:@\"Yeah\" style:UIBarButton
well you need to go with a background image and with title and
// Creates a back button instead of default behaviour (displaying title of previous screen)
UIBarButtonItem *backButton = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"back_arrow.png"]
style:UIBarButtonItemStyleBordered
target:self
action:@selector(backAction)];
tipsDetailViewController.navigationItem.leftBarButtonItem = backButton;
[backButton release];