Unlock Black Costume:
Complete the game with a 100% completion.
Unlock Classic Costume:
Download and start the 'Rhino Challenge' DLC.
Unlock Cross Species Costume:
Complete the game on any difficulty setting.
Unlock Scarlet Spider (2012) Costume:
Find the fountain which is located near the middle of Central Park. Then, go north until you reach the middle bridge, which is directly at the center of Central Park. If you look on the right side of the bridge you will see a Spider-Man emblem. When you take a picture of the emblem the Scarlet Spider (2012) costume will become unlocked.
Added by: Sanzano Jun 29th 2012, ID#4718