This was the prototype of that one Ai wallpaper. Unlike the Yuu's, this one wasn't been that much different other than the phone and tablet are larger and it has slighty different shading.

Note: This was probably mistakenly named as "完成壁紙.jpg" which is used for finished wallpapers and the final wallpaper that was used is tagged "最終ラフ.jpg" which is used for prototypes. I checked the psd of the finished wallpaper, which had the same filename as this wallpaper but it was PSD file and it had the post #828 in it. The PSDs doesn't have any data from the prototypes of the wallpapers.