I can see your sense of balance between black and white ; repetition in composition is a good idea ( in my universe, at last ; I'll be much more critical about the choice of poses. At the beach the girl is with a very natural pose, in the street more "posed " but ok. Also her arm is made too black by the treatment, it appears at a thin stick at first glance. And I dont like at all the pose on the mirror, artificial and bored, and the use made of deepness of field is poor : the details of the room ( like door, something on the floor ) are too much there. And I hardly see the need for the white stripes in your overall composition. So keep working on the concept, make it simpler and stronger. So sorry to be a bit negative on this, just go on ! And thank you for using my stock and linking back.
Playing around with GIMP; putting layers on top of each other and playing around by changing the layering mode and shifting the images slightly was how I started; then I ended up cutting parts of the images out and laying them on top of each other, and also one of *Aspartams patterns, playing around with the layering modes and the opacity, stuff like that.
This one was really a quick experiment, basically just trying different things and then cutting pieces apart and putting them together in different ways, throwing out a lot of stuff. I was looking for a kind of balance rather than a picture, so I used that as an excuse not to do tedious things like remove background.