The wallpapers on this collection must accomplish at least 3 conditions:
1- Must be portrait/vertical designed (the standard resolution for work well on any phone is 1080x1920px)
2- Must be designed to be mostly true black (#000000). As it turns out, OLED displays actually turn off the individual pixels that are meant to display true black, thereby giving an infinite contrast ratio which makes pictures look more vibrant. Plus, it can save power and it's easier on the eyes in lower-lit environments.
3- Wallpapers must be at least 45% True Black.
4- The design must not be colorful or confusing in the upper top part and the bottom part. Take in count that in phone this parts are where the icons bars and notification bars are displayed and many people uses transparent bars with just icons, and a lot of colors or shapes in this zones can be confusing. Keep it clear.

WALLPAPER ENGINE for Phones can be downloaded from here:
https://www.wallpaperengine.io/android/