There are three secret pictures you can unlock and view in the gallery. Go to Althena's Shrine after you get Kyle. Talk to the woman on the right. It is a picture of Jessica. After you lose Nash and get the engine for the ship, go to Iluk and talk to the man in the top right house. It is a picture of Mai. The last picture is unlocked after killing the final Boss. Go to Ramus' shop and talk to him. It is a picture of Luna.