I have a HTC 8X phone and install a new 8.1. version. One of news of this version:
Tile background on Start screen- Tiles fit together like puzzle pieces to display the full image.
I have read a manual, but it doesn't helps. I can make all what is writting, but at the end - black screeen :(
Background photo on lock screen I cant change too.
And be aware that if you have an "empty" space on the start screen you also will not see the picture and if the app till is not transparent you also will not see the picture.