We saw many cyclists riding the Ring Road in Iceland. Most bicycles were loaded with front and rear panniers and packs on the rear rack. I have no idea if their goal was to ride the entire ring road, or if they each had a separate destination in mind.
We also saw one unicyclist as he walked his bike up a 10% grade, near Vik I think, but I was too slow to photograph him, or notice many details. We saw him again the next day as we returned to Reykjavik. He was a little further down the road and cars thankfully were giving him a wide berth as he wobbled along with a full pack on his back. Alas, still no picture, but you have to admire his spunk. This road would be challenging enough on two wheels, never mind one.