This is the method used to unlock the special illustrations found in Gallery Mode.

Illustration	How to unlock
Special Illustration 1	Automatic
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