Probably the strangest volume hand antics of any thereminist ever, were those of Paula Mary who played on the 1950's TV show, YOU ASKED FOR IT. Her technique is a bit bizarre and her instrument (an RCA) was waaaay out of alignment and its pitch had slipped way below where it should have been, but all things considered she played very well.
http://www.youtube.com/watch?v=MFLWDYVZAno
I have two pieces of general advice on volume hand movement. These are my own thoughts & opinions and in no way reflect the opinions of the management.
1. Avoid dipping toward the antenna on every note. There is an increasing number of thereminists who do this. They seem to believe that it is necessary in order to separate the notes and overcome the theremin's often annoying portamento, but unfortunately it also disconnects the notes. This gives a jerky, staccato "beep-beep" feel to everything they play.
Here is a video of thereminist Kip Rosser playing the Lennon/McCartney standard, BLACKBIRD. The volume hand is highlighted in this performance and you can see that every note is staccato. This is an artistic choice but I would argue that anything you do all the time, on every note, on everything you play, is bound to become irksome no matter how skilled you are at doing it. I'm not trying to criticize Kip specifically, I'm sure he is a fine artist, but this is a perfect illustration of something I think all thereminists should carefully consider.
http://www.youtube.com/watch?v=Qt8_W6sc5Wo
2. Stay away from unnecessary movements that you may seem prompted to make but that do not directly affect the sound. One of the keys to good (and pain-free) precision theremin playing is EFFICIENCY and ECONOMY OF MOTION. The best way to produce the sound you want is going to be the simplest way.
The longer we persist with a bad or unnecessary habit, the harder it becomes to get rid of it. Constant repetition over several years will create pathways in the brain that are inextricably connected so that you can't get rid of the habit without interfering with your ability to perform the task it is associated with.
There was a very famous opera singer who would go noticeably cross-eyed on high notes. She tried to avoid doing it because it didn't look good on TV but she found she couldn't hit the notes!