Definitely you get this file name
This is the Button Click who Choose the Photo From Your Phone
private void ImgPicker_Click(object sender, RoutedEventArgs e)
{
PhotoResult photoresult = new PhotoResult();
MessageBox.Show( photoresult.OriginalFileName);
}
Just Copy And Paste this code.
In the Messagebox you Get the File Name.
or if you want to more Details About image Than Check This Referance
http://www.mindscapehq.com/blog/index.php/2012/02/28/windows-phone-7-working-with-camera-tasks/[
^]
Enjoy...