diff --git a/dynamic_background.api.php b/dynamic_background.api.php
index 54e764f..a1c7744 100644
--- a/dynamic_background.api.php
+++ b/dynamic_background.api.php
@@ -50,4 +50,18 @@ function hook_dynamic_background_weight() {
   return array(
     'weight' => -30,
   );
-}
\ No newline at end of file
+}
+
+/**
+ * Customize the image selector display.
+ *
+ * @param $form
+ *   A nested array of images, and other settings, as returned by
+ *   dynamic_background_image_selector_form().
+ * @param $settings
+ *   The settings that will be used to display the image for this object.
+ * @param $instance
+ *   The {dynamic_background_usage} record for this object.
+ */
+function hook_dynamic_background_selector_alter(&$form, $settings, $instance) {
+}
diff --git a/dynamic_background.module b/dynamic_background.module
index c91de12..25fd993 100644
--- a/dynamic_background.module
+++ b/dynamic_background.module
@@ -637,6 +637,10 @@ function dynamic_background_image_selector_form($type = 'default', $data = -1) {
   drupal_add_css(drupal_get_path('module', 'dynamic_background') . '/css/dynamic_background.theme.css', 'module');
   drupal_add_js(drupal_get_path('module', 'dynamic_background') . '/js/dynamic_background_selector.js', 'file');
 
+  // Allow other modules to modify the form above using
+  // hook_dynamic_background_selector_alter().
+  drupal_alter('dynamic_background_selector', $form, $settings);
+
   return $form;
 }