The hallway in a rental I had years ago had one bare stretch of wall between the bathroom door and a radiator that never quite worked, and nothing I owned fit it until I pinned up a plain old poster, the kind you'd buy for a few dollars and frame later and then never frame. It looked better than the art I'd actually paid for in the living room. That's the moment it clicked, not in some grand room with good light, but in a leftover bit of wall nobody plans around.
Posters sit easiest with furniture that doesn't ask for attention, a plain painted wall, an old dresser, a lamp that's seen some use. They don't need a gallery wall or a matching frame family to look right, which is the whole point of them, honestly. I've got one taped up with the kind of tape you're not supposed to use on painted walls, next to a proper framed print that cost ten times as much, and the cheap one is the one people ask about. They work because they're casual, so put them near things that are a little casual too, a stack of books, a chair with a blanket over the arm, not a room that's trying hard.
They're at their best in rooms you live in fast, a bedroom, a kid's room, a stairwell, a first apartment where you don't know yet if you're staying. Morning light through a thin curtain does something nice to a poster that a spotlight never will, it just glows a bit instead of looking lit up for inspection. They suit a rented place, a studio, a dorm, a house that's still becoming itself, and they suit any season really, though I notice mine more in winter, when the light's low and flat and the color on the wall is doing more of the work than usual.
Where they don't belong is anywhere trying to look finished and expensive, a formal dining room, a front hallway meant to impress, next to furniture with real age and good joinery, where a thin sheet of printed paper just looks thin by comparison. I tried one over a chest that belonged to my wife's grandmother once. It did not go well. Measure your wall space before you commit to a size, because a poster that looked generous in the package often looks apologetic once it's up.