Mimic tile interface of Win8, but on the diagonal — got idea from a 2015 WP theme called Photo Me and another called Linstar.
Have same sort of shadows, as though each of the elements is floating above the surface. Perhaps have the stuff in the lower right corner a little smaller, jammed a little further into the corner, and then a angled gradient, from transparent to solid white (solid right at the corner), to provide some contrasting background for the text when the movable elements slide underneath.