So for me it depends on my room.

In the office/gaming room, the walls are entirely full of gaming related and other geeky posters. Some fantasy maps, a discworld map, such stuff. Posters of the Persona 5 palaces.

For the living room, one wall has a small area with cat pictures (including of my baby cat of 12 years who died 2 months ago <3), the main wall is slowly creeping full of empty board game expansion boxes where I put the stuff into the main box and then hang the expansion box up with poster strips to decorate the wall with the board game shelf.

For the bedroom, the main wall has the images from the two Sunstone calendars with the calendar parts cut off. The whole room is red/black, so they fit really well, plus the theme fits.