Okay now that you've seen it, THEORY TIME
We know that the top right corner is Eternalia, right? Yes. But I think the three buildings represent the three "original" councillors. The blue one being Kenric because he's a telepath and it's in the front(he was always her favorite) and the purple one being Oralie because she was always the least noticed to Sophie out of the three and now Sophie is ignoring her.
THAT LEAVES BRONTE AS THE GREEN ONE. Not only does that building LOOK like it has pointy ears, but it's the most included in the picture. Bronte has ALWAYS besn the councillor she payed attention to the most, whether it being out of fear or trust, and recently he's been the most included in her group (on missions and stuff).
BUT IT'S GREEN. Like, WANDERLING GREEN. I have a theory on Instagram (councillor_bronte) that he's gonna die in one of the last books, and this would just prove it even more.
In conclusion, I'm scared, the cover is amazing, and I don't want my boy to die.
Also, why was Gildingham one of the places she chose? THAT confuses me.