Fitness Trainer,
If I were designing your flyer I would focus on results rather than your head shot. Although it might help differentiate you from other trainers, the head shot should be played down and the benefits should be played up.
I would start with a professional photo of a healthy, energetic, physically fit person either working out or admiring the results in a mirror. The copy would include bullet points addressing the benefits of choosing you to be their trainer, as well as a few testimonials and your contact information. It would be short and sweet, but concise and powerful.
You can easily set yourself apart from the average trainer with a well crafted flyer, which, by the way, could be adapted for use as an ad, mailer, brochure, etc...
Best of luck!