The very last paragraph of the GIRM gives perhaps the best advice: “Every effort should be made to ensure that . . . the canons of art be appropriately taken into account and that noble simplicity come together with elegance.”
The bishops of the United States have published guidelines for church art and architecture that also touch on seasonal decoration, Built of Living Stones. It says that seasonal decorations should “draw people to the true nature of the mystery being celebrated rather than being ends in themselves.” They should also “enhance the primary liturgical points of focus,” that is, the altar, lectern, and presider’s chair. (Enhance, not overwhelm!) And it gives a few specifics: Living flowers and plants are preferred to artificial greenery; seasonal decorations should remain throughout the whole season; traditional objects such as Advent wreaths and Christmas cribs should be proportional to the space; banners are most effective when they do not carry words (including joy, hope, and peace).
When this document discusses art in general, though, it offers a great deal for those who decorate to ponder: “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.”
That may seem a lot to ask of a few poinsettias or a banner or two, but even these humble additions to our churches should point us toward prayer and praise.
Noble simplicity with elegance. Quality. Appropriateness. Not rules. But great guidelines, don’t you think?