John Carey regularly posts amazing photos and makes them available as wallpapers for iOS and Mac devices. Also, he spent a good amount of time figuring out just the right size of a photo for use in iOS 7 so it looks best with the Parallax effects. His iOS parallax pack has a slew of beautiful images.
I tend to change my iOS wallpapers every month or so, and these collections give a lot of options to keep things fresh. The wallpaper on my Mac changes automatically every hour, so these images show up throughout my day and offer a nice change of scenery.
There are a lot of ways to get these images onto your iOS device, such as Dropbox, email, or even visiting these sites in Safari. Once you’ve saved a photo to your Camera Roll, you can easily select one as a wallpaper from the Photos app. The Use as Wallpaper option is available in the Send To section.
The simplest way to change the wallpaper on your Mac is to right-click on the desktop and click Change Desktop Background. You can add a new folder of images by clicking the + button in the left side of the window. Make sure the folder that you made after downloading these new images is in a good location before adding them here. After you add the folder, just click on the image you want to be your new background. You can also check Change picture to automatically rotate through the folder every so often.