Spend the indicated type of credits to unlock the corresponding concept art:

Creatures 1: 1 Blue credit, 1 Gold credit, 3 Red credits
Creatures 2: 2 Blue credits, 1 Friend credit, 2 Gold credits, 3 Red credits
Samus: 2 Blue credits, 1 Gold credit, 3 Red credits
Storyboards 1: 2 Blue credits, 1 Gold credit, 3 Red credits
Storyboards 2: 2 Blue credits, 1 Friend credit, 2 Gold credits, 3 Red credits
World 1: 1 Blue credit, 1 Gold credit, 3 Red credits
World 2: 2 Blue credits, 1 Friend credit, 2 Gold credits, 3 Red credits