Thanks for all the comments so far! I really was just looking to satisfy my curiosity, not ask for advice on how to convince my wife to try new things. I will admit, though, that this thread has started to inspire me a bit…
As I mentioned before, my wife and I were both virgins when we got married. And you don’t get to be 37 (or 34, for her) and still remain a virgin without being seriously boring people, believe me. Fortunately, being boring is like eating garlic – as long as you both do it, it’s fine…
My “decision” to remain a virgin was largely a product of a strict religious upbringing, which continued to influence my feelings of what was “right” or “comfortable” long after I abandoned religion. For her, it’s purely a matter of culture; where she grew up, people just do not have sex before marriage, period. She tells me that this attitude is changing as China belatedly enters the 20th century, but for her, like me, it became a deeply ingrained attitude.
One difference between us is that I have been exposed to the wonderful world of pornography and have always wondered about what it would be like to have sex in various positions, whereas she has NEVER been exposed to pornography and thinks that the Missionary position is the only “normal” way to have sex. I don’t complain, since I enjoy having sex with her any way we do it, but I do worry that she may not be getting as much out of it as she could, and I have to admit I still wonder what it would be like to try other positions (especially “doggy-style.” for reasons I don’t quite understand)
Anyway, after having read the comments so far, I decided to try talking to my wife about it. I told her that I had been doing some research on how to have more enjoyable sex, especially when the man is not particularly well endowed. When I first mentioned that maybe we could try doing it with me behind her, she was horrified because she thought I was referring to anal sex. I assured her that wasn’t what I meant, and then she was worried that I wanted to have sex standing up (which I certainly wouldn’t mind trying, but not what I was talking about). I told her that I didn’t want to make her feel uncomfortable, and if we tried something that she didn’t like, we wouldn’t have to do it again. She agreed, but she was a bit tentative and I didn’t push her on it right away.
We don’t have a lot of time for sex during the week due to the fact that we both work crazy hours and I have to get up a lot earlier than she does in the morning. Which is to say we do have sex during the week, but it’s often a bit on the rushed side and not conducive to experimentation because we’re both exhausted and she worries that I’ll be too tired in the morning. But we don’t have any plans for this weekend… 
Barry