For a realistic looking scene
deterministic positions often looks bad. On the other
hand too much randomness is also not 'realistic'. What
you need for object placement is controlling randomness.
Below are three examples. First image displays a grid
made irregular by disturbing the positions with an
uniform random jitter. Overlapping can be controlled by
adding only a small amount of jitter.
Next an uniform random placement.
The disadvantage of this strategy is that overlapping can
not be controlled.
Last an example with Poisson disk
sampling. The term 'disk' means that there is an
avoidance radius to control overlapping.