Accent Lighting - Flat Pictures

[kenna]

It's been a while since I've posted, but my studio is taking off and I am ready to invest in more and better lights. I am currently using an Alien Bees 400 with a soft box with reflectors. I'd like to add some dimension to my shots by adding a backdrop light (I'm currently trying to do this rather unsuccessfully with a flash and umbrella), and a hairlight or some other "directional" light. As you can tell from my terminology, I'm learning more from trial and error than from textbooks, but hopefully you can catch my drift. To illustrate what I mean by "flat" pictures, and to show the result of my current lighting setup, I'm attaching a photo I recently did for a client. Thanks for any advice on the lights, and I don't mind any comments on the photo (although I'm not asking if you don't want to give any).
Kenna