I've seen multiple people(example: Twins Turboo) with "five star" castles. I'm assuming that's from the new castle skins. If there are tiers to getting your castle from zero to five stars, please inform me on how to do so. (I would of included an image, but I got an error) thank you for your time.
The upgrades are via special bundles/packs you can buy marked for castle skin upgrades. Not sure if the special item is in a loot drop or event prize anywhere yet. Maybe someone else can chime in about where else to get them