This is just a quick post (I hope) with a tip on how to render a different background when using HDRI lighting in Blender 3D. As you can see from the images on my gallery I generally just render a single object and don't really make a scene for it. The downside of this is that if the object is reflective it doesn't have anything to reflect in the empty scene and looks plain and unrealistic.
Like others, to get around this problem I use HDRI maps to give fake reflections. The problem with this is that you then have the HDRI image in the background which can take focus away from the original image, to get around this you can make a plane in the background which blocks out the HDRI image, but it often has to be quite large to fill the whole camera background.
A workaround which I use is to use the Blender's compositor to composite in a different background from a different scene in the blend file. Of course this could be done afterwards if you just rendered a PNG with transparent background, but if your not intending to do any post on it anyway you might as well do this in Blender. For example, I normally use a simple blended background found in the 'World Settings' giving a gradient effect, which I would rather use than the HDRI background but still have the benefits of the reflections the HDRI provides.