An Experiment and figured out that It can save about 7.6% battery life/hour at 20% brightness by using a power save wallpaper on an AMOLED Screen display.
Tips: On an AMOLED Screen black colors are generated by turning off the backlight/pixels, creating a dark pixel. A pixel that is turned off does not use any power. Therefor the more black, the more battery power you save.(Just For AMOLED Screen, Make sure your phone has an AMOLED screen).
Power Save Wallpaper Only For OLED Screen.
Such as POLED Screen and AMOLED Screen and so on.