A yard full of cars is a yard full of customers' goods that aren't moving. Unless, of course:

It's empties waiting for a customer's call
It's storage in transit - otherwise known as a warehouse with wheels

And many other possibilities for the picture, including but not limited to:

It's waiting for arrival of more locomotives rendered surplus by PSR
It's a posed picture of a yard that's just completed but not opened yet
It's an interchange yard with another carrier that's just been cleaned out