So the background returned just like Dilopho and Carno in Season 2. That's a huge spoiler, by the way.
Anyway the next STAGE is gonna be the Thorny Canyon, featuring:
-Carnotaurus
-Medusaceratops
-Pentaceratops
-Styracosaurus
-Tyrannosaurus
-Phuwiangosaurus
-Giganotosaurus
-Sauropelta