Last fix for GTK+3.5

usr/share/themes/Lubuntu-default/gtk-3.0/gtk-widgets.css

@@ -861,8 +861,9 @@ GtkIconView.view.cell:selected:focused {
 /*********
  * image *
  *********/
-GtkImage {
+GtkImage,
-    background-color: @transparent;
+GtkImage:insensitive {
+     background-color: @transparent;
 }
 
 /***********
@@ -940,6 +941,14 @@ GtkImage {
     -unico-inner-stroke-width: 1px;
 }
 
+/*********
+ * label *
+ *********/
+GtkLabel,
+GtkLabel:insensitive {
+    background-color: transparent;
+}
+
 /********
  * menu *
  ********/