Added some diagrams

Author: javiereguiluz

_images/form/form-custom-type-postal-address-fragment-names.svg

@@ -106,7 +106,9 @@ any :doc:`existing form types </reference/form/types>` because they are too
 different. Consider an application that wants to reuse in different forms the
 following set of fields as the "postal address":
 
-.. TODO: illustration of the form field
+.. raw:: html
+
+    <object data="../_images/form/form-custom-type-postal-address.svg" type="image/svg+xml"></object>
 
 As explained above, form types are PHP classes that implement
 :class:`Symfony\\Component\\Form\\FormTypeInterface`, although it's more
@@ -177,10 +179,10 @@ in the postal address. For the moment, all fields are of type ``TextType``::
                 ])
                 ->add('city', TextType::class)
                 ->add('state', TextType::class, [
-                    'label' => 'State/Province/Region',
+                    'label' => 'State',
                 ])
                 ->add('zipCode', TextType::class, [
-                    'label' => 'ZIP/Postal Code',
+                    'label' => 'ZIP Code',
                 ])
             ;
         }
@@ -250,7 +252,7 @@ learn about all you can do with these options::
         public function configureOptions(OptionsResolver $resolver)
         {
             // this defines the available options and their default values when
-            // they are not configured explicitly when using the form
+            // they are not configured explicitly when using the form type
             $resolver->setDefaults([
                 'allowed_states' => null,
                 'is_extended_address' => false,
@@ -417,10 +419,13 @@ by overriding the ``getBlockPrefix()`` method in ``PostalAddressType``. The
 second part of the Twig block name (e.g. ``_row``) defines which form type part
 is being rendered (row, widget, help, errors, etc.)
 
-.. seealso::
+The article about form themes explains the
+:ref:`form fragment naming rules <form-fragment-naming>` in detail. The
+following diagram shows some of the Twig block names defined in this example:
+
+.. raw:: html
 
-    The article about form themes explains the
-    :ref:`form fragment naming rules <form-fragment-naming>` in detail.
+    <object data="../_images/form/form-custom-type-postal-address-fragment-names.svg" type="image/svg+xml"></object>
 
 .. caution::