What makes mobile wallpapers work
A lock screen is a glance, not a gallery visit. You unlock your phone dozens of times a day and see the wallpaper for about a second, usually with a clock sitting on top of it. That is why the strongest portrait backgrounds put their subject in the lower two thirds and leave the top third as breathing room — sky, water, fog or a plain gradient all do the job.
The other constraint is hardware. Modern phones are taller than 9:16, so an image that fills a classic ratio will be cropped on a tall display; keeping the important detail centered and away from the very top protects it. Darker scenes have a practical bonus too: on OLED screens, dark pixels are switched off, so a deep navy night sky is gentler on battery than a full-brightness white sand beach. Neither trick requires software — just a prompt that plans for both.


