What are your rights if someone takes a picture of you?

You can always ask the person that took the picture, to please delete the picture, that you do not want your picture taken.

There are usually signs posted, in some cases, the signs are to alert you that by being at the location you agree to have your picture taken.
In other locations, there could be a general right to privacy, i.e. a locker room, lobby, but even in these cases there are security cameras taking video.