Here's the official cover for Vol 9.
From what I guess in the background, there is a clear blue sky so that might be a setting for the climax.
Each novel except for the first volumes of a 2 volume arc have the background from the climax of the novel. The part one of the 2 volume arcs show where the spirit was first met. For e.g. in Vol 3, Shidou meets Kurumi in a classroom and the background for the cover was the classroom.