Enter the Creation Hall on the Village Map, then hold L and press X, Y, B, A(2). A sound will confirm correct code entry. The Astronaut, Knight, Ninja Girl, Spartan, and Supergirl templates will be available.
Bonus music tracks
Collect the hidden Pirate Coin in each level to unlock the three "?????" songs at the bottom of Isaac's item shop list. The songs are "Opening Credits", Mayor Rosa's "Light Of My Life", and the ending song "Real Life".