Random scatter of a box within certain constraints set in 3ds MAX compound objects.
Rendered with Light Tracer
image above: the 'lighten' effect is used with a concrete as the background map and brightness and contrast is adjusted 
'Difference' effect with bricks.jpg as foreground image. Effect is mostly controlled by the 'fill = %' of the foreground image.
hyphothesis:
1.'difference' effect gives a very interesting "revealing effect" or somethng that is emerging
2. Still can't think of any use for the 'darken' effect except as background images. Old t-shirts graphics?
