I think the Wall-E one would be very difficult to pull off because we can't use textures or colors even to create the feel of the whole barren trash covered planet thing.

Light intensity in relation to fall off would of course be scene scale dependent, if the bulk of the objects in your scene are on average oh i dunno say 20 units away and the light is dying off at around 15 then yeah that won't work. The usual problem with cranking up the intensity however, is that it overexposes surrounding objects by the point it actually illuminates the scene. You can see it on your campfire logs. In this case, since we're only using the gray lambert, the mia_exposure lens shader shouldn't be so troublesome, give it a whirl, it'll clamp down those over-brights and you'll find you can do A LOT more with your lighting and even some contrasting and such.

Ooh maybe you can make a few more soccer balls to represent pebbles around the larger rock and a few thin planes for grass?