You can do it via the ambiance options.first you make the desired wallpaper with the n9 size which is 840x480(not accurate but you can google it).i think it must be .png so it will be recognized.after you have done it you go to the ambiance settings section “Ambiance Wallpaper” and choose Apply.Firstly create it for Application by choosing the created wallpaper from before(restart themedaemon) then make the same steps for homescreen and you should have your desired ambiance.i hope i was clear but can't explain it better.that's how i do it so it must work for you too
Hope i helped.