If dream signs are recurring themes, then fictional characters from series I like, or other references to some game/anime ect. are one of them… a huge amount of my dreams feature them, can be anything from meeting and talking to a character to seeing a picture of them somewhere in the dream. What exact series it is changes, but it’s commonly video games or Homestuck, and sometimes the same one repeats over a period of days… (for a while I had lots of Ace Attorney-related dreams). Only a few of my dreams are completely free from those. So fictional characters in general is the biggest one, I think, especially since this has been true for most of my dreams the last years.
Also, video game worlds or themes. It can be playing a game that I haven’t played(so the dream makes it up) or doesn’t exist, or being in a world that just feels like a 3D platformer game level (with powerups, coins, platforms ect.) even if nothing about games are mentioned.
Being in places I have never been to, or that I have been once but would have no reason to be at the time. Also, when at “my house” or another place I know, it rarely is how the house actually looks like, the room is completely different.
A bunch of my dreams also switch between 1st person and 3rd person perspective at random points, but not sure if this can really be counted as a dream sign, or just something that happens to everyone.