Clean Up Images only removes images that are no longer being used so you can free up space. There is a separate option to clear the cache. You also don't need to keep a backup of it. Actually I would advise against that. LaunchBox will automatically re-create it, but because the cache was created and wasn't refreshed when you added the images, LaunchBox doesn't know there are new images to be found. Refreshing the cache makes LaunchBox see there are manually added images, then start to cache them and show them. When you download metadata and media through the import process, or when you scrape afterwards, LaunchBox already automatically refreshes the cache so that the new images show up, but you need to manually refresh it when you manually add in new images.