Every plan and RCP view has a view property called View Range, also known as a visible range. The view range is a set of horizontal planes that control object visibility and display in the view. The horizontal planes are Top Clip Plane, Cut Plane, Bottom Clip Plane, and View Depth.
 

As their names imply, the top and bottom clip plane represent the topmost and bottommost portion of the view range. The cut plane is a plane that determines at what height certain elements in the view are shown cut. These 3 planes define the primary range of the view range.

The functionality to use a background image while rending used to be available in earlier versions of Revit.  The new Mental Ray rendering engine includes the ability to create a generated sky and sun but if you need to show a specific background or site the ability to add an image is no longer available.   

There is an alternative that you can use to get a background image in your rendering. 

You can export the Rendering to a TIFF format which exports the sky as a separate alpha channel.  This makes replacing the sky in an image editor much easier.  You can use Photoshop or any other image editors that read and write the TIFF file format. However, this can be a little bit extra work and requires another program.  

There is a way to get around this problem and do this all inside of Revit.

When plans aren't showing what you want i.e. not cutting through the building elements you want to see cut, try using the often overlooked Plan Region tool.

Located on the View tab on the Design Bar, the Plan Region tool allows you to specify an area by sketch, which you can set a different View Range to that of the rest of the plan.