It is not a very good idea to try modifying the UIAlertView's height/width or add a UIImageView to it as this might result in your app getting rejected by the App Store. However, ios-custom-alertview is a good alternative.
A sample code would be:
CustomIOS7AlertView *alertView = [[CustomIOS7AlertView alloc] init];
[alertView setContainerView:yourSubView];
[alertView setButtonTitles:[NSMutableArray arrayWithObjects:@"Close", nil]];
[alertView show];