Pumpkin with a maltese cross cut into it with letting inside. Pumpkin with a firehelmet on it with lettering. Firetruck on the back with ghosts/monsters inside as firefighters. Skull with it's mouth open with the maltese cross in it with or without lettering. Pumpkin on the back with the dept.'s logo cut into it. Skull on the back with open mouth and logo inside.
Course you could always just make your dept. shirts however you have them, and make them orange and the lettering in black. City 20 minute away from me got pink shirts and left everything else the same as regular duty shirts for breast cancer. Don't always have to think totally out of the box, you can keep it simple.