The best tool for this situation is the randomize transform tool. It's not a tool that has a shortcut key and it's buried in the object menu (Object > Transform > Randomize Transform), so the easiest way to access it is to simply search it using Space.
To create the wall from that image, do the following:
Create a plane for the wall.
Duplicate a few cubes around
Use the randomize transform tool and set it to affect the location of the objects (except the axis along the wall) and the scale of the object. Something like this:
Create a big cube as a particle system and define an cubic (or any shaped object) as particle. Use volume as emitter and turn off "render emitter" and change the default halo to object, select your cube. Play around with the settings in physic for different particle behaviour...