>> metre rule if you are a poseur
I take exception to that comment :-) I like my 1m stick.
A rucksack? How big's your rucksack? You could place an Action Man rucksack by a small stone and get really distorted pictures! A better option would be to place somebody else's Action Man by the stones.
A kid or love one in an occasional shot is fine by me. Scale is massively important and anything that portrays that is great. The problem comes when the photo is more person than site.