You can use whoever's tori you want.
And no, you may photoshop images, draw them free hand, do whatever you like. But I must stress this once more:
Create a "camera-style" snapshot of your character (tori/uke/whoever) doing something sinister. We want you to capture them in the act so we can bring a full scale attack down on them! See Event Banner for example.
Just as if you were looking out of a camera to capture the naughty moments. (Or a sniper scope like in the banner :P)