In ancient castles, the lords of the manors hung tapestries on their walls. The heavy, decorative pieces were woven to reflect meaningful scenes, but in reality, says Touch of Tapestry, they were designed to keep the cool, damp castles warmer.
You can do the same thing in your basement by hanging yards of heavy fabric on the walls of your castle. Gambrick says to treat the fabric like you would wallpaper and begin by making glue. Mix a tablespoon of corn starch and ¼ cup of cold water together. Set it aside. Separately, boil 4 cups of water, then add the corn starch mixture to the boiling water, which you’ll continue to cook over medium heat for an additional minute. (Add sugar, chocolate, eggs, and a few other yummy things, and you have pudding like this chocolate pastry cream from Mashed. Just kidding!) Back to the glue, cool it for a bit then pour it into a spray bottle to use as wallpaper glue. If that’s too much bother, you could staple the fabric to the wall or hang it from the ceiling.
The fabric wall covering, while not likely to be an inexpensive option, will be a creative one that lets you add your own flair. If you hang the fabric from rods, it’ll be easy to change as the spirit moves you.