At first glance, they appear to be textures of Rikku from Final Fantasy X and the Prince of Cannock from Dragon Quest II (whom I have affectionately dubbed "Kukki"). When opening pack.dat in Game Graphic Studio, they are images 299 and 300 respectively. They are the first textures to appear in the group of character textures used in speech bubbles, despite not having expressions. This means they may not have been playable, but may have been NPCs. Morrie, Quistis, and the Chance Card NPCs use a single face as well (Torneko has a separate iris texture that moves independently of his face).Sorry fans, no hints of Yuna anywhere.
In addition, this text was located amongst the column names when making purchases in the shop. I believe it says 交換済 (Already Exchanged), but its small size makes it hard to read. I am unsure if this is even unused, but if it is it may have been used before the idea of the 'SOLD' stamp came into play.