Perhaps because customs differ throughout the world, the Church has few rules regarding decoration of sacred spaces. Common sense and respect for the congregation should guide all decisions, as should regard for the General Instruction of the Roman Missal, which reminds us “to ensure that . . . the canons of art be appropriately taken into account and that noble simplicity come together with elegance.”
The United States bishops have prepared a document, “Built of Living Stones,” that provides reflections on ecclesiastical architecture and art, as well as decorations for liturgical seasons. The document states these decorations should “draw people to the true nature of the mystery being celebrated rather than being ends in themselves.” In addition, “quality art draws the beholder to the Creator,” and “appropriateness is demonstrated by the work’s ability to bear the weight of mystery, awe, reverence, and wonder.”
The document also observes that Christmas crèches should be a size appropriate to the space they occupy. These days many churches erect Nativity scenes in an area removed from the sanctuary, so size is unimportant. Other documents reference the location of the crib in a church. There is nothing definitive about a manger’s placement before or beneath the altar, but it must not detract from the altar itself or the sacred mysteries celebrated on it. Therefore, it is preferable for it to be situated elsewhere in the the church.