BTS Live Wallpaper 4K is a free app that allows you to use a variety of different wallpapers for your lock screen and home screen. If you're a big fan of the BTS (also known as Bangtan Boys or Bulletproof Boy Scouts) and want to have a personalised mobile device, then you'll definitely want to check out this app. It has a ton of different wallpapers, and you can even use your own images for your lock screen and home screen. The best thing is that the BTS Live Wallpaper 4K app is free, so there is no need to pay a penny to download it.