Like any other Android phones, you can easily change wallpaper on HTC One. There are 3 options to set new wallpaper: Live Wallpapers, from Gallery, default HTC Wallpapers. Learn How to Change Wallpaper on HTC One:
1. Open "Settings" App (You can drag down the notification bar and tap Settings icon)
2. Select "Personalize" and then tap "Wallpaper"
3. There you have the 3 following options:
a. HTC Wallpapers: There are some default preset wallpapers and you can select among them
b. Live Wallpapers: choose among the available live wallpapers (both downloaded and defaults)
c. Gallery: Choose an existing photo from photo gallery (You may need to crop the photo)
4. Apply the process and enjoy the new wallpaper