Selecting one of initial random wallpapers to evolve makes it the most fit one in the current population, giving it the biggest chance to crossover (exchange genetic material with another wallpaper). Wallpapers also mutate with small random chance, and can be easily downloaded.
You can find more details in this blog post: building wallgen.
Wallgen is an evolutionary wallpaper generator using genetic algorithm to create never ending list of abstract ambient wallpapers. It was built during my 1-project-a-month meta-project in February 2017.
You can play with live version here: http://szymonkaliski.github.io/wallgen.
Code is open sourced and available with MIT license here: szymonkaliski/wallgen.