We expect the attractive balance of the Renaissance and even slavish symmetry post Sir Christopher Wren* in our architecture and are surprised when it is repeatedly violated in earlier buildings. But they were as aware of it as much as we are, they just put it farther down their priority list. If you needed an alcove to put in a special chapel, you just put in an alcove on that side. If someone needed another alcove later they natural gravitated to the matching spot on the other side, but if they never needed one, that was no problem. They wouldn't move an altar a foot to the side, but if it needed to go to the 2/3 mark, that was pretty too. St Magnus in Kirkwall has got a few sections where they moved a wall in a foot or out a foot because of practical considerations. It's still solidly symmetrical, though

There's that ubiquitous red sandstone again, that they built everything from. It's a soft stone, so when they started using it for gravestones, families found that the were becoming weathered and unreadable. Richer people started sending for more durable stone, even when the bones were interred indoors. Sometimes people would put up a wooden marker in anticipation of greater wealth later. I found this Memento Mori fascinating. It is much like a sign for a shop.
The sandstone stills shows signs of being painted over during the English Civil War in the 1640s. Whatever illustrations the Catholics had were now forbidden, to be replaced by plaques commemorating human beings or groups of them, which the Reformers considered Less Idolatrous.
You get things like memorials to the war dead, which includes their family identifiers, including this one I found humorous.
Much better than pictures of Biblical stories, sure.
A note on Saints and local gods: Learning two unrelated eras side-by-side can suggest associations you might not otherwise have had. When Orkney was Catholic, the center of its authority was in Rome, a place where few people had ever been. Being able to have your own bishop gave you a chance to send someone you knew to represent you among the great and the wise. The idea was echoed at royal courts as power consolidated and kingdoms grew larger. Having an earl who was married to one of the king's relatives gave you an avenue to be heard. This would have been even stronger before general literacy, but even now, we want someone of our own to advocate for us. God gave other tribes pictures, but to the Jews He gave the captions, rather forcing them to focus on words, which traveled better and were more universal. Yet we iz who we iz, and the Jews got idolatrous about the words themselves, and Christians gladly and self-righteously followed. It's a step toward abstraction, but it's not foolproof. Jews had Kabbalah, pre-Christians had runes, and Christians dabbled in grammarye, leading to Baptists putting Bibles on secondary altars with a single light shining down on it. For all of them we must say "Not thus, but thank you for your assistance." Asking a saint to pray for you is not that different. When we destroy one idol we secretly build another.
Where was I? St Olaf, who is big in Norwegian thinking and thus in early Orkney, was a pagan convert to Christianity. His statue in the Kirkwall cathedral has interesting symbolism. And there's that stonework again.
If you look at the serpent he is crushing, it has a human head. The face is in fact his own, representing the death of his old self, or perhaps the constant need to keep killing it.
The scratching is a mason's mark showing which person cut the stones in this section. There is an identical mark from a very close time in the Cathedral of Durham in the north of England.