My favourite recurring theme in my dreams is probably the vast yet empty landscapes: I frequently dream of plains and similar places that stretch on endlessly, typically with some sort of mountain or forest not very far away, but there is almost never anything to see within said barren plains - when there is, it's typically very small in comparison to the rest of the fields, and is almost always inanimate. I think this emptiness grants a sense of liminality and comfort.
As for yourselves, what are some recurring things in your own dreams that you can recall? What do you think of them?