Well... I mean for exactly as shown as on desktop... Including if you use live wallpaper, then your lockscreen wallpaper will has live wallpaper.
I've made this wallpaper for lockscreen as dummy (find it in zip file attachment). So you just save it in your sdcard and set it as lockscreen wallpaper and you'll see your desktop wallpaper as lockscreen wallpaper.
I've tested it in MIUI, I don't know if it will work also on other rom, but it might be work.