Background is a beautiful, well designed and easy to use Unsplash client, in which you can browse and save high quality photos. Saved images can be used among other things as a wallpaper as they are under Creative Common Zero License which means you can copy, modify, distribute and use the photos for free, including commercial purposes, without asking permission from or providing attribution to the photographer or Unsplash. 
Save a picture by touching and holding it. 
Background is free, but with an in-app purchase you can buy Background Premium, which turns off the unobtrusive ads, unlocks the search and. 
There are 5 basic screens (the order of which can be changed and screens can be hidden): 

  • search (requires Background Premium),
  • newest photos,
  • curated photos,
  • favourite photos (requires Background Premium),
  • settings. See more photos by scrolling down or up. You can change the screen by swiping left or right.

Background was featured multiple times by Apple in the App Store.