Some pretty interesting shots. On something like that where do you have the light source placed? Is it just the regular indoor overhead lights or also some side lights from desk lamps? I think I like the third one best.
I have the glass bowl suspended about 30cm above the background that I am using (which sits on the desk) so I have a Speedlite (Yongnuo YN560) which is illuminating the background only. In this kind of thing where the actual subject is pretty much transparent, you should light the background and not the subject itself.