This fixture is not IRender Ready, but making it so is not difficult.
First, I'm going to hide the lamp shade to make it easier to add an IRender nXt bulb.
The lamp does include a component for the bulb, but this component is not a light source, so I'm going to remove it.
IRender nXt includes several bulb types including Point (an omni directional light source), Spot, and Beam. For this fixture, a Point light is appropriateBefore adding a bulb to the model, review and set the options to match the actual lamp you're modeling. When you CLICK "Create/Place" and add the bulb to the model, take a little time to adjust the position.
The Presets tab on the Edit Material dialog includes "Shade" - render settings that are intended for lamp shades.
The preset values for Shade are available on the Trans tab.
Transparency is set to 50, so 50% of the light produced by the bulb will get through this material.
Transluscency is set to 1, so anything behind the material will not be clearly visible.
For a detailed description with a few examples on the rendering behavior of Transparency and Translucency, read this Render Plus Article
Here's the new light fixture included in a rendering:
The most efficient way to make a new light fixture, or to make a component downloaded from the 3D Warehouse IRender Ready, is to modify the component and add a bulb or bulbs from the IRender nXt library.