No, it is impossible for T-mobile to charge you just for taking pictures on your phone. Even if they wanted to they would have no way to monitor your picture taking. From a legal point of view they are also not entitled to charge you for taking photos because you are not using their service in any way when you take the photos, you are only using your hardware.
When you send the photos by MMS or e-mail they can charge you because you are using their internet (GPRS) service.
If you send the photos by bluetooth or infra red they can not charge you because you are sending by direct transmission to another cell phone nearby, again you are not going through their network services.