From Eyrbyggja Saga : Thorolf Goes To Iceland :
Thorolf established a great farm at Hofsvag which he called Hofstad, and had a large temple built there with its door in one of the side walls near a gable. Just inside the door stood the high - seat pillars with the so - called holy nails fixed in them, and beyond that point the whole building was considered a sanctuary. Inside the main temple was a structure built much like the choir in churches nowadays, and in the middle a raised platform like an altar. On this platform lay a solid ring weighing twenty ounces, upon which people had to swear all their oaths. It was the business of the temple priest to wear this ring on his arm at every public meeting. There was a sacrificial bowl on the platform too, with a sacrificial twig shaped like a priest's aspergillum for the blood of animals killed as offerings to the Gods to be sprinkled from the bowl. Inside the choir - like part of the building the figures of the Gods were arranged in a circle right round the platform. Every farmer had to pay a tax to the temple.
Adam of Bremen had this to say about the interior of a temple: ( From a supposed eyewitness account from King Sweyn )
In this temple, which is entirely decked out in gold, the people worship the statues of three Gods in such ways that the mightiest of them, Thor, occupies a throne in the middle of the chamber, Wotan ( Odin ) and Frikko ( Freyr ) have places on both sides. Thor they say, presides over the air, which governs the thunder and lightning, the winds and rains, fair weather and crops. The other Wotan, carries on war and gives to mankind strength against his enemies. The third is Frikko, who bestows peace and pleasure on mankind. His image has a huge phallus. Wotan they sculpted armed, as our people are wont to represent Mars. Thor with his scepter apparently resembles Jove. For all the Gods there are appointed priests to make offerings on behalf of the people. If plague or famine offend, a libation is poured to the idol of Thor; if help in war is needed, to Wotan; marriages are the realm of Frikko.
Kjalnesinga describes Thorgrim Helgason's temple this way :
In his hayfield he had built a temple that was one hundred feet long and sixty wide. A temple fee was extracted from all those from the area. Thor was the most honored God. On the inside it was rounded , and there were windows and hangings on the walls. The statue of Thor stood in the center of the great room, with the other Gods on either side. I their front was a wooden altar which was covered with iron. On this altar burned a sacred fire that was never to be extinguished. On the altar was a silver armband, which the Godi would wear whenever suits were brought. Everyone had to swear their oath upon this armband. A large copper bowl stood on the altar, and into this bowl went the blood given by animals or men to Thor. This blood was then sprinkled over the men and animals in attendance. The animals that were sacrificed were then used for the sacrificial feast that followed. Men who were sacrificed were thrown outside into the well known as the well of sacrifice.
The final description ( though brief ) is in Heimskringla :
King Olav now went into the temple with a few of his men and a few of the bonders, and when he came thither where the Gods were, he saw Thor sitting there, most honored of all the Gods, and adorned with silver and gold. It then goes on to tell of the destruction of the temple which I do not wish to discuss.
Though the sources are varied there are common themes in each of the stories. The altar and statues always seem to be in the middle of the floor. Thor is the main God, and is placed in the center with the other Gods on either side of him. The one constant is a blood sacrificial bowl to hold the blood and though not always stated the twig to sprinkle the blood on those of the kindred. The other main theme in these stories is the arm - ring that was worn by the priest at all functions, and that all who came before him came to place their oath upon.
Though these brief descriptions do not give us a full view of the inside of our ancient temples, they do at least give us a glimpse into the way that they might have looked. The rest we will just have to leave up to our imagination and interpretation !
Go with Odin's wisdom, Freyja's love and Thor's protection !