Successfully complete the indicated task to unlock the corresponding concept art 
at the "Extras" menu:

Creature Concepts: Collect all treasures. 
Environment Concept Art for Arctic Sea and Amelia Concepts: Successfully 
complete Arctic Sea Expedition. 
Environment Concept Art for Coastal Thailand and Alister Concepts: 
Successfully complete Coastal Thailand Expedition. 
Environment Concept Art for Croft Manor and Doppelganger Concepts: 
Successfully complete Croft Manor Expedition. 
Environment Concept Art for Med Sea and Amanda Concepts: Successfully complete 
Mediterranean Sea Expedition. 
Environment Concept Art for Mexico and All Men Concepts: Successfully complete 
Southern Mexico Expedition. 
Environment Concept Art for Ship and Natla Concepts: Successfully complete 
Andaman Sea Expedition. 
Environment Concept Art for Jan Mayen Island, Gear, and Artifacts Concepts: 
Successfully complete Jan Mayen Island Expedition. 
Game Flow Storyboards: Successfully complete the game on the Master 
Survivalist difficulty. 
Lara Concepts: Collect all six Relics. 
Zip and Winston Concepts: Successfully complete the Prologue.