1 - "Sly" ... I'll be the first dissenter. It's not bad, but the background is distracting. Wider aperture would have cleaned it up some, or using a simpler background.
2 - "Mystique." I'm sorry, but I'm not mystified. Really, you've got more of a mischeivous look than a mystical look. Photographically, it's a pretty good shot -- good background, good sharpness, it works. The problem is that the composition draws your eye to the other girl. The scarf/boa/thing seems like an attempt to connect you two, but it doesn't quite work, imho.
3 - Sensuous -- You look unhappy. Very unhappy. The small mouth, the angled-down face, the dark eyes -- it says unhappy to me. And I'll second the lighting comments from above. It looks like flash-shadow around the left side, and it's pretty distracting. The other note is composition -- your face is centered. Ideally, the photographer would have placed your face off-center, so that you (rather than the background) fill the image, and the viewer's eye is led across your body to your face. The below cropped image should illustrate that.
4 - Untitled, looking back over shoulder - Good modelling work, bad photographer. Your pose is nice; I won't go into detail, but it works fine. The lighting, however, is just awful, I'm sorry. Mostly washed out, big shadow in lower right, with no contrast across your face.
I hope that helps, and that I'm not too harsh -- you've got a great start, but you need a better photographer.