What's up with the Black Butler intermissions?
I'm late to this, whoops.

But the tarot cards, I assume, are just a foreshadowing of the uprising events.
If the Death tarot card appears: what happens in the episode?
Well, obviously, death. Either, on Ciel's side or the opponent of Ciel.

Some other cards are harder to explain but you could search up "insert tarot card here" on Google and then find the meaning there. 

Sorry if this wasn't much help. I tried!