I did some research on the matter and of course the answer to this question is pretty subjective and also a matter of style. Generally it is recommended that a chandelier hang anywhere from 30" to 36" above the tabletop in a room with an 8-foot ceiling. Then the opinions start to vary. Some designers feel that you should add 3" to the suspension height for every foot above the standard 8 feet where as others still believe that 30-36" is still the recommended height regardless of ceiling height or room size.
When not hanging a chandelier over a table, the general rule of thumb is 7 feet above the floor. I think when hanging anything, you should hang it where it looks best and mind not to hang it too low where people may bump into it. Also remember the lower you hang a fixture the bigger it will look and the opposite is also true, the higher you hang it the smaller it will appear. So it is also important to take the size of the room into consideration in proportion to your fixture.