How to add wallpapers to iOS 7?

No :(

The list of Apple wallpapers in Settings → Wallpapers & Brightness → Choose Wallpaper → Apple Wallpaper → Dynamic or Stills is not customisable by the user, without jailbreaking.

If you want a separate list of wallpapers, you can create an album in the Photos app, add your wallpapers to that album, then open that wallpaper in the Choose Wallpaper → Photos list.

No. The only (non-jailbreak) way to add wallpaper is by selecting it from a photo album or Photostream.

However, once you have chosen the wallpaper and/or lock screen, you can delete the image from your Photo collection.