The folder LeftOrRight.tar.gz contains two files:

1. LeftorRight.png, which is the wallpaper (1024*76
2. LeftOrRight,svg, an Inkscape .svg-file, in case you want to alter some things.

I am not sure wether this is eyecandy or not. Maybe it is some kind of an optical illusion.
Look at it for some seconds, look aside and look again at it and try to find out wether the square falls to the left or to the right.