This all depends on the type of pic, the source of the pic, and the manner in which the pic are being used. For example, if you have posted a pic of yourself on your website, and the web site is publicly accessible, and/or if you did not provide a disclaimer that all posts were your private property and any duplication or reproduction thereof required written permission, and/or you did not copyright the pic and/or there is not a watermark on the pic indicating ownership and/or you did not take precautions to prevent unauthorized download, duplication or reuse.....then I am afraid you will have a difficult task. However, if someone took a pic of you without your knowledge and is using it without your permission for promotion or in a lewd manner, you may have options.
If the picture was taken from a public place, such as on a road or a park, then, there is little you can do. The fact that they are taking the photo in public means that is already photograph that can go onto the internet, for the public to see, since anyone could have been there and saw just what the camera saw. If they entered your house where you can expect privacy, then they are violating your right to privacy and you can hire an attorny and force them to remove the picture.
Even if you took a photo of yourself and had it on a public website, that does not give anyone the right to distribute it elsewhere. If you took the photo, you automatically have the copyright as soon as it's made. Your best course of action is to contact the person, and the site administrator and tell them the photos of you are unauthorized, unless the person distributing them can prove that they own the copyright (as in they took the photo, or you signed over rights), then they'll have to remove them or you can press legal action. Whether you want to spend the money on legal fees or not, that is another story.