How to customize appearance of UISearchBar

// Search Bar Customization
// Background Image
[self.searchDisplayController.searchBar setBackgroundImage:[[UIImage alloc]init]];

// Backgroud Color
[self.searchDisplayController.searchBar setBackgroundColor:[UIColor redColor]];

// Search Bar Cancel Button Color
[[UIBarButtonItem appearanceWhenContainedIn: [UISearchBar class], nil] setTintColor:[UIColor whiteColor]];

// set Search Bar Search icon
[self.searchDisplayController.searchBar setImage:[UIImage imageNamed:@"search_ico.png"]
                                forSearchBarIcon:UISearchBarIconSearch
                                           state:UIControlStateNormal];

// set Search Bar textfield background image
 [[UISearchBar appearance] setSearchFieldBackgroundImage:[UIImage imageNamed:@"search_box.png"]
                                                forState:UIControlStateNormal];

// set Search Bar texfield corder radius
UITextField *txfSearchField = [self.searchDisplayController.searchBar valueForKey:@"_searchField"];
txfSearchField.layer.cornerRadius = 10.8f;

By IOS 5.0 you have the chance to use

  [[UISearchBar appearance] setSearchFieldBackgroundImage:[UIImage imageNamed:@"searchbar.png"]forState:UIControlStateNormal];

Here is some common properties you can change to customize UISearchBar:

Here is the solution I was looking for: Subclassing a UISearchBar, & overwriting the method layoutSubviews

- (void)layoutSubviews {
   UITextField *searchField;
   NSUInteger numViews = [self.subviews count];
   for(int i = 0; i < numViews; i++) {
      if([[self.subviews objectAtIndex:i] isKindOfClass:[UITextField class]]) { //conform?
        searchField = [self.subviews objectAtIndex:i];
      }
   }
   if(!(searchField == nil)) {
       searchField.textColor = [UIColor whiteColor];
       [searchField setBackground: [UIImage imageNamed:@"buscador.png"] ];
       [searchField setBorderStyle:UITextBorderStyleNone];
   }

   [super layoutSubviews];
}