It's interesting that searches for general concepts (Countryside wildflowers, airplane scenes, train scenes) seem to work pretty well, while searches for specific characters (Ponyo, Yubaba, Porco Rosso) return negligible results.
Most of the descriptions generated for the images are likely generic and doesn't contain reference to the actual characters and names. I might explore incorporating some sort of more movie specific description in the metadata of the image to improve queries for specific characters.