Does wallpaper affect battery life?
Live wallpapers could potentially kill your battery in two ways: by causing your display to have to light up bright images, or by demanding constant action from your phone's processor. On the display side, it may not matter much: your phone requires the same amount of light to display a dark color as a light color.
What wallpaper uses less battery?
If your smartphone boasts an AMOLED display, then applying black coloured wallpapers will help you save battery life. This is because pixels that make the AMOLED displays only utilize battery power to illuminate light colours and don't need any energy to show black colour.