It was proposed for the reredos of a somewhat narrow but high ceilinged church. It would have been executed in secco fresco on plaster. This is a very old technique which allows the artist more time to finish details and complex designs in contrast to true fresco which must be done in wet plaster and with a continuing plastering day by day on the areas that the artist can complete in one day. If you examine the Sistine ceiling you can see the lines of each batch of plaster.
In secco fresco there are no lines as the plaster is done all at once before the painting begins. The ancient Egyptians used a form of secco fresco, so it's a long-ago method. Today, I would use acrylic with a matt finish, which would be a piece of cake compared to true fresco.