Using the code you showed there, you could set the modalTransitionStyle property of imagePickerView. But, your possible values are (from the SDK documentation):

• UIModalTransitionStyleCoverVertical: When the view controller is presented, its view slides up from the bottom of the screen. On dismissal, the view slides back down. This is the default transition style.
• UIModalTransitionStyleFlipHorizontal: When the view controller is presented, the current view initiates a horizontal 3D flip from right-to-left, resulting in the revealing of the new view as if it were on the back of the previous view. On dismissal, the flip occurs from left-to-right, returning to the original view.
• UIModalTransitionStyleCrossDissolve: When the view controller is presented, the current view fades out while the new view fades in at the same time. On dismissal, a similar type of cross-fade is used to return to the original view.

Your other option requires you to get a lot fancier. Let s assume the navigationController is the the root view controller of the application, and it s stored in a property of your application delegate called navigationController. You could implement the following methods:

- (void)curlInViewController:(UIViewController *)viewController {
    self.curledViewController = viewController;

    [UIView beginAnimations:@"curlInView" context:nil];
    [UIView setAnimationTransition:UIViewAnimationTransitionCurlDown forView:self.window cache:YES];
    [self.navigationViewController.view removeFromSuperview];
    [self.window addSubview:viewController.view];
    [UIView commitAnimations];
}

- (void)curlOutViewController {
    [UIView beginAnimations:@"curlOutView" context:nil];
    [UIView setAnimationDelegate:self];
    [UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)
    [UIView setAnimationTransition:UIViewAnimationTransitionCurlUp forView:self.window cache:YES];
    [self.curledViewController removeFromSuperview];
    [self.window addSubview:navigationController.view];
    [UIView commitAnimations];
}

- (void)animationDidStop:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context {
    if([animationID isEqualToString:@"curlOutView"]) {
        self.curlViewController = nil;
    }
}

This is now easily available in OS 3.2 and above; you do it like this: --

// if the legend button is tapped, curl up the map view to display the legend view underneath. 
- (IBAction) legendButtonPressed:(id) sender
{
    UIViewController *legend = [[LegendViewController alloc] init];
    legend.modalTransitionStyle = UIModalTransitionStylePartialCurl;
    legend.modalPresentationStyle = UIModalPresentationFullScreen;
    [self presentModalViewController:legend animated:YES];  
    [legend release];
} 

I love these dormant questions. I had a lot of success doing something like this where you use a view transition animation to show the new view and then presentModalViewController in the completionHandler so that your new view is treated as a modal view.

    UIView *container = self.view.window;
    [self.theNewViewController viewWillAppear:YES];
    [UIView transitionWithView:container
                  duration:kAnimationViewTransition 
                   options:UIViewAnimationOptionTransitionCurlUp
                animations:^{
                    [self.navigationController.view removeFromSuperview];
                    [container addSubview: self.theNewViewController.view];
                } 
                completion:^(BOOL finished) {
                    [self presentModalViewController:self.theNewViewController animated:NO];
                }
 ];