How to Build a Pirate or Dungeon Loot Room
Pirate Theme
Start with Pirate Chest and Dread Pirate Chest as the centerpiece containers. Add an Eye Patch to your outfit and place a Skull and Crossbones block on the wall. Use Crate and Moldy Crate for secondary storage so the room reads as a ship's hold. A Gold Skull Chest fits the theme as a rare reward container. If you want a trap, place a Pirate Chest Mimic Spawn Egg near a real Pirate Chest so visitors cannot tell them apart.
Dungeon Theme
Use Bone Chest, Skull Chest, and Ironbound Chest as the main containers. Place Cobblestone Gravestone, Cobblestone Cross Gravestone, and Cobblestone Tombstone around the edges, and add a Cobblestone Gravestone Spawner to keep the area active. Strangle Vines and Spanish Moss break up the stone. A Cauldron Chest or Infernal Chest works as a focal point.
Locking the Loot
Secure the best container with a high-tier lock such as Onyx Lock, Ruby Lock, or Diamond Lock, and keep the matching key on your Key Ring. Place a Pilferer's Lock Pick in a hidden spot as a backup. If you want the room to feel dangerous, add a Bound Soul Spawn Egg or Skeleton in a side chamber.