good photos of people are valuable and I would highly reccomend. In lieu of good photos taking skills, take lots of photos with a fancy camera on an automatic setting. (lots = 100+ per person)

In different poses, in different places, outdoors, indoors, looking at or away from the camera, pulling happy, normal or other expressions.

some relevant information: http://blog.okcupid.com/index.php/the-4-big-myths-of-profile-pictures/