Unlock the following Special Illustrations at the Gallery menu by performing the corresponding tasks:
SPECIAL ILLUSTRATION - HOW TO UNLOCK Special Illustration 2 through 5 - Beat Survival level 500. Special Illustration 6 - Unlock all EX characters. Special Illustration 7 - Unlock all Gold/Shadow characters. Special Illustration 8 - Unlock all arcade ending art. Special Illustration 9 - Unlock all EX ending art.
To unlock EX characters, defeat the Shadow version of a character in Survival mode. Then, highlight the character at the character selection screen and press Plus. EX characters will also be unlocked after playing 48 hours.