upload you wallpaper image / music file* into your album. You can create a hidden album for it. *trial account and 3G/unlimited users can upload mid format music 50MB/500MB/1000MB can upload mid, mp3, wmv music format file.*

View the full image, copy the image URL under the image.

paste the URL into your album properties' "background image" / "background music" field and save the change.*