Artist would use their art as shrines or offerings to the gods in hopes of serving their path towards righteousness. Art was also used as representation of stories to remind the followers of the path they are taking. In almost all Catholic churches you will see The Passion of Christ somewhere in the church. That reminds everyone why they are in the church, and who they are worshiping. The Passion of Christ shows what Jesus did to save us from out sins, and that helps others realize visually what he gave up.
Another version of spiritual art is judgement and the afterlife. The Egyptians believed heavily that in the afterlife the would be reborn. The pyramids were a large representation of art to serve as a grave for leaders who have passed away. Pyramids were sacred places with fine art inside that served as a connection for the dead to the afterlife. The Egyptians would place sculptures in the pyramids for the dead to take the shape of.
Spiritual art is a part of our history whether or not one is religious. It has guided and changed the way we view and create art. One cannot go through art history without religions art. Art is what it is today with the creation of religious