you could try something like this: http://vimeo.com/5147726 and then randomising the rotation and scale with a script if things look too uniform? i remember doing the set dressing tutorial video from digital tutors and using a similar method to place rocks on a beach.
Does this explain it better? Or is it just retarded? :D 400th post btw. Woooho, fuck yeah! :D [EDIT] Rewrote the text. Don't make tutorials 2.30 in i morning :D