Open the Settings app
Tap Wallpaper
Tap Choose a New Wallpaper
Tap the wallpaper category you used (e.g., Dynamic, Stills, Live, or Photos)
Select the wallpaper you want to remove
Tap the wallpaper preview
Choose Set Wallpaper
Select Set Both (or Lock Screen / Home Screen as needed)
Repeat for any other screen (Lock Screen and Home Screen)
To remove a custom photo wallpaper: open the Photos app
Find the photo used as wallpaper
Delete the photo from the Photos app (this removes it as a wallpaper option)
If you still see it as a wallpaper: go back to Settings > Wallpaper and select a different wallpaper for each screen