The sculpture is showing a cube or a ball depending on the view angle.
Print in red for a Christmas tree decoration.
Print the 6 parts of the plate "cube_ball_illusion.stl" file.
Assemble them as shown in the pictures. (Printed in PLA with a 0.34 nozzle, Slic3r 0.9.7)
Use a string to put in on your Christmas tree.
Or just play with some different combinations.