In the past I very often used the awesome harmony script from Rayflectar:
(Image by Rayflectar!)
to introduce some random translation / scaling / rotation to certain objects or blocks, mostly to make it look more natural.
Unfortunately the scrip is not working anymore in R7, so I wonder if anyone out there might have a easy to use alternative. I am sure it might be a rather easy thing to do in Grasshopper but it is ,so I learned in the last 2 hours, over my abilities.