add bgimage style for halloween

packages/app/src/components/Theme/ThemeHalloween.module.scss

@@ -26,12 +26,19 @@ $light: lighten($secondary, 10%);
   }
 
   // add background-image
-  #page-wrapper,
   .page-editor-preview-container {
     background-image: url('/images/themes/halloween/halloween.jpg');
   }
 }
 
+.theme :global {
+  .bg-image-wrapper {
+    position: fixed;
+    width: 100%;
+    height: 100%;
+  }
+}
+
 //== Light Mode
 //
 .theme :global {