Accent Lighting - Flat Pictures

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

It looks to me like your key(main) light is the only source here. Where is the reflector placed? I'm guessing to the models left and back a bit.
I think your problem is you've got them too perfectly balanced. The reflector side should be darker. Back it off so there is, say, a stop difference from the key light. This will give you the definition you're looking for (the other ideas would help as well). Youjust want to open up the shadow side not balance it perfectly (unless you want flat light of course).
Hope I've helped, i'm no expert.

Yeah, a nice shot, but you're not going to get any more depth unless you make some changes to your setup. Sure, another light will help, but it's not absolutely neccessary.

First, even if you kept the light and reflector the same as this shot, a light or even dark gray bg paper would let the sillouette shape of your subject show. That automatically would give the shot more depth.

Also, if you move the flash/softbox more to the side, or even slightly behind the model, it will produce a rim effect, seperating her from the bg. Then use the reflector (or fill if yuo get another light) to open up the shadows on the side away from the key.