In this case there is quasi-religious imagery but you as the reader aren't actually supposed to be mystical about the god/devil in the story the way the characters themselves are. It's not C. S. Lewis
Do you also find LeGuin uninteresting?
Catholics (and other denominations too) consider the three transcendentals to be Truth, Goodness, and Beauty, which are all natures of God†:
* https://en.wikipedia.org/wiki/Transcendentals
This philosophical/theological thinking goes back to (at least) the Middle Ages:
* https://plato.stanford.edu/entries/transcendentals-medieval/
So the fact that "decoration" would be present is unsurprisingly, as Beauty in this reality can help to lead to greater reality of Truth and Goodness as well. It's why there have long been traditions with art, music, architecture, etc, in Catholic culture.
† God is Truth, God is Goodness (itself), and God is Beauty. (God is Love as well.)
There's a whole crazy universe of occult-like lore within Catholicism that a subculture of Catholics really get into, it's pretty wild, often quite macabre.
I have a couple of those types in my family. The way they talk about praying to specific saints is like they're paladins in an RPG using divine magic.
Then there's the whole thing where the church has bones of long dead saints encased in ornate reliquaries that supposedly dispense miracles.
