good angle and a wonderful subject. if you want to add more drama, create space and try this one again, but don't center the subject in the frame. definitely use the rule of thirds here. i would draw the subject off to the left and lower in the frame, then zoom out just a bit. it would make the subject look smaller, defensive and more vulnerable. and that would lead the viewer from the gag to her eyes and then to the empty space to the right. it would give the viewer something to think about... besides just a pretty face wearing a ball gag. remember, pictures tell stories.