Roll white fondant thin and use flexible polyblade to cut varying lengths of 1" wide rectangles. These will be used to make the broken 3D lines on the top tier. Allow pieces to dry overnight.
Prepare and stack cakes. Using a small ruler or straight-edge, mark off vertical lines top to bottom on the 8" cake. Use the black royal icing in a bag fitted with tip #2 to outline the vertical lines then draw horizontal lines in a stained-glass looking pattern. Brush piping gel into the outlines using the flat brush.
Attach fondant pieces to top tier using piping gel. Outline pieces with black royal icing then brush colored piping gel into pieces.