diff --git a/picture.module b/picture.module
index 19cff5b..6286bd9 100644
--- a/picture.module
+++ b/picture.module
@@ -1990,9 +1990,19 @@ function _picture_image_style_url($style_name, $path, $timestamp = NULL) {
     $url = image_style_url($style_name, $path);
   }
 
+  $token_query = array();
   if (!empty($timestamp)) {
-    $url .= (strpos($url, '?') !== FALSE ? '&' : '?') . drupal_http_build_query(array('timestamp' => $timestamp));
+    $token_query['timestamp'] = $timestamp;
   }
+
+  // Allow other modules to alter the token_query for the given style.
+  drupal_alter('image_style_uri_token_query', $token_query, $url, $style_name, $path);
+
+  // Append the query string with the token, if necessary.
+  if ($token_query) {
+    $url .= (strpos($url, '?') !== FALSE ? '&' : '?') . drupal_http_build_query($token_query);
+  }
+
   return $url;
 }