The first thing I check on a poster is the white border, or whether there even is one, because that tiny margin changes how it sits once it's framed. A poster with a clean quarter inch edge lets you float it inside a mat without the image getting cropped weird, and one that bleeds right to the edge of the paper needs a frame with no mat at all or you lose part of the picture. I learned this the slow way, bought a print with no border, stuck it in a mat frame I already owned, and ended up with the top of someone's head missing. Small thing, but it tells you a lot about how much care went into the printing.
Posters earn their place in rooms that need a bit of personality without a lot of commitment, a rented bedroom, a hallway that's otherwise just a strip of white wall, a home office where you look up from a screen fifty times a day and want something other than a calendar to land on. They work best in groups or as one large piece that fills real space, because a single small poster on a big wall just looks lost, like it wandered in from somewhere else. A living room with high ceilings can take a large single print above the couch, while a smaller apartment wall often looks better with two or three mid sized ones spaced close, giving the eye somewhere to travel. Seasonally they're forgiving, nothing fades a poster faster than direct sun through an uncovered window, so a north facing room or one with curtains that actually get closed is the safer home for anything you care about keeping sharp.
Check the paper weight before you buy, run a finger along the surface for texture, and if it arrives rolled in a tube, flatten it under books for a day or two before framing or it'll fight you the whole time. Look at the corners too, cheap printing shows up first in a soft or blurry corner where a sharp one should be. Where posters fall short is permanence, they don't carry the weight of a real painting or a family photo wall, and in a room meant to feel settled and grown up, too many of them side by side can read more like a dorm than a home. They also don't love humidity, so skip the bathroom unless it's framed behind glass.
This is the right call for a home that's still becoming itself, where the walls are allowed to change their mind every year or two.