Android: Apps like Wallpaper Changer will rotate the wallpaper on your Android device at periodic intervals, but you have to select the images for it from your gallery. If you want some fantastic high-res images as your background, get them automatically from 500px with 500 Firepaper.
The free app lets you choose where to grab images from 500px across feature lists (popular, upcoming, editor's choice, fresh today, fresh yesterday, fresh this week) or categories (animals, film, concert, black and white, nature, landscapes, food, travel). You can set the update interval (in time or on every time you switch off the screen), brightness, and whether to use parallax effect. Finally, choose whether you want to update the images only over Wi-Fi or not -- a smart choice because those high-res images will eat into your data allowance.
You can't save any of the images, and can show one for a maximum of 24 hours. Portrait and landscape images are different and the app has a preset cache limit of 256MB.
500 Firepaper (Free) [Google Play]