As you continue to Level Up in Festival Plaza, when you speak to Captain Sophocles in the Castle, you will be offered a New shop or facility to add to your Plaza. If you choose not to add any, you will given an item such as a Pearl, Big Pearl, Nugget or Festival Ticket. However, there are several additional Special Bonuses you will receive at given Levels.
Level: Special Bonus
Level 4: Ability to play Missions is activated
Level 8: You become able to acquire New Stores from other players
Level 10: You can now order the clothing of other players if you don't own it.
Level 20: You can now change the name of the Festival Plaza.
Level 30: You can now get enhanced services in Shops. (After Defeating Elite Four)
Level 50: You can now change the appearance of the castle. (Glitz Theme)
Level 60: A New castle theme is available. (Fairy Tale)
Level 70: A New castle theme is available. (Subdued)
Level 100: The "I reached Festival Plaza Rank 100!" greeting becomes available.
After defeating the Elite Four and hitting Level 30 in Festival Plaza, you will unlock many New items and services in your Shops. After defeating the Elite Four and hitting Level 40, in addition to that, you will gain the ability to change the music that plays while in your Festival Plaza. (Can be changed by speaking to the Construction Worker inside building.)
Different Music Themes
Music 1: Festival Plaza Theme
Music 2: Hau'oli City Theme
Music 3: Hau Theme
Music 4: Konikoni City Theme
Music 5: Malie City Theme
Music 6: Iki Town Theme
Music 7: Paniola Town Theme
Music 8: Po Town Theme
Music 9: Seafolk Village Theme