A few things that come to mind...
Junk yard office/shack.
Maybe a weigh scale.
Fence around the perimeter - something solid too, so your little plastic people who live nearby don't have to look at the "eyesore".
Some sort of backhoe or crane or something to move the junk around?
An old beat up truck that belongs to the owner, and is used to collect and/or deliver junk.
More junk.
A junkyard dog & dog house
You have got some really nice looking piles of junk - rusty, but not too much...!
Andrew