Unlock the following concept art at the "Extras" menu by performing the corresponding tasks:

CONCEPT ART - HOW TO UNLOCK
Creature concepts - Collect all treasures.
Environment Concept Art for Arctic Sea and Amelia concepts - Complete arctic sea expedition.
Environment Concept Art for Coastal Thailand and Alister concepts - Complete coastal thailand expedition.
Environment Concept Art for Croft Manor and Doppelganger concepts - Complete croft manor expedition.
Environment Concept Art for Med Sea and Amanda concepts - Complete mediterranean sea expedition.
Environment Concept Art for Mexico and All Men concepts - Complete southern mexico expedition.
Environment Concept Art for Ship and Natla concepts - Complete andaman sea expedition.
Environment Concept Art for Jan Mayen Island, Gear, and Artifacts concepts - Complete jan mayen island expedition.
Game Flow Storyboards - Complete the game on master survivalist difficulty.
Lara Concepts - Collect all six relics.
Zip and Winston Concepts - Complete the Prologue.