Here is a really well done website, Images of the Ara Pacis, with detailed text and many photographs of the Ara Pacis. The site appears to be the work of a student at Bluffton University. Unfortunately for her the lighting conditions seemed to be a little less than optimal the day she took her pictures and some of them are just dark overall (you may take photos in the museum but no flash is allowed), but the site is still a great resource.