I've got a HUGE library of great-looking photos that I've been turning into iPhone wallpaper images. Since I'm doing it for me, I figured I'd post them for YOU in case you wanted to use them, too.
The top one is for iPhone 4S and the bottom is for iPhone 5 and up. You should be able to save it to your phone's camera roll, and from there, set it as wallpaper.
This edition features a flag at the Hoover Dam on the Arizona / Nevada Border. I liked the contrast between the colors of the flag, the rugged look of the rocks, and the bright blue sky.