The Digital Deluxe Package includes:

• The original soundtrack composed by Karl Flodin + lots of bonus tracks.
  
• An art booklet with concept art, deeper lore on in-game characters and thoughts on the game's design.
  
• A hand-drawn comic by Y/CJ/Y in a Lovecraftian semi-autobiographical style about the making of Sea Salt.
  
• A few desktop backgrounds.
  
• The whole map of the peninsula with descriptions (not found in-game) of each area.
  
• And the official posters and stickers in high resolution (so you can print them yourself).

Important: Nothing is changed or added to the actual game. This is all just extra content outside of the game, which can be found in the game's folder.