Character mode: complete Story mode.
Hard mode: complete Story mode.
Sound Library voices: complete Character mode.
Complete the indicated task to unlock the corresponding picture in the gallery:
Picture 1-1: complete the game eight times and select the squares at the end.
Picture 1-2: insert the Game Boy Advance game Fullmetal Alchemist: Omoide No Sonata in the cartridge slot.
Picture 1-3: insert the Game Boy Advance game Full Metal Alchemist: Hagane No Renkinjutsushi in the cartridge slot.
Picture 2-1: complete Character mode with Ed without continuing.
Picture 2-2: complete Character mode with Al without continuing.
Picture 2-3: complete Character mode with Mustang without continuing.
Picture 3-1: complete Character mode with Armstrong without continuing.
Picture 3-2: complete Character mode with Scar without continuing.