I don't know if that can work with your existing objects, since I haven't tried it myself, but maybe for future projects this tool could come in handy ? http://www.scriptspot.com/3ds-max/scripts/stone-placement-tools Sry, if you already know about it :)
Yea paint scatter in Graphite is pretty good, my personal favorite is Neil Blevins (soulburn scripts) object paint. You can also use reactor to scatter or pile up objects, he covers that on his site too. Particle flow and reactor can be a bit unpredictable and hard to dial in if you're wanting something very specific.…
Are you using 2011? Object Paint might be what you're looking for? [ame] http://www.youtube.com/watch?v=ZwHJgfdOFDw[/ame] You should be able to do all you need here. I'm not sure if it will randomize them as you place them to the extent you're looking for, but you could just as easily clone them a few times and…