Each iOS update for your iPhone and iPad has had a brand new flagship wallpaper since iOS 1, then called iPhone OS.
First of all there were the Fish and the Earth. With iOS 4 came the ability to change the background on your home screen, and not just the lock screen.
iOS 11 introduces 17 new wallpapers built into the settings app. With 4 returning wallpapers from older iOS versions.
One of the returning wall papers is the default black from iOS 1-3 for the homescreens. Other returning wall papers are, he Earth in full few, and the waves from iOS 9 and iOS 10.
New wallpapers include the new wave but with a beach. Flowers with different back grounds. The moon, and Earth at Night. Finally there are a selection of wallpapers give a nod to the famous Apple rainbow. Featuring stripe across the screen on other plan back grounds.