The Stonehearth Creative Bundle contains:

• The Stonehearth OST
  The OST is 3.5 hours of Raj Mann musical goodness, containing 73 .mp3 tracks.
  
• The Stonehearth Artbook as a .pdf
  The Artbook is 51 pages and contains sketches, concept art & final illustrations from the development of the game.
  
• A Stonehearth digital poster
  The digital poster is a 3840 × 2160 .jpg that can be used as a desktop background or printed out. (@300dpi it's 12.8in × 7.2in)

Note: After purchasing the DLC, it will automatically download to the same folder as the game content. You can find it by right clicking the game in the Library and selecting Properties > Local Files > Browse Local Files.