Ok, time for a few bad jokes.
Welp, I guess the detective (smokes cigarette) is already dead.
Also from that end-of-chapter-roster I guess everyone's on the table... figuratively, for now, but quite likely literally, later.
More on topic: I'm actually surprised that even little Ai is featured on the card, moreso than in Natsuki's case.
My guess is also that the empty/crossed out field is for the entity that killed the teacher back then (and probably at least Rina recently).
When the curse idea was first mentioned (as Tokiko cursing someone to death and paying with the lives of those around her) I had already thought that it might be actually the other way around and she's living "on borrowed time", that others are dying in her stead, so to speak. Like that teacher, for instance.
No no no. You get Natsuki off that card right this instant. Also, I'm assuming Rena is still alive. No body means no death, so she is probably the ninth picture. And since the body count is shooting up all of the sudden, I'm guessing the "murder curse" probably actually the grandpa's death. Maybe Rena killed him.
Rina's body is the one Tokiko identified, remember?