As I remember the Game Rainbow Six Vegas 2 I have has a webcam capture method which took 3 pictures of your head
That could be rather disturbing, considering the kinds of things griefers already do with custom sprays in games like TF2.
I was wondering if it was possible to make my players in a game looks like my friends from real picture.
Do you want this to be a development time thing (your friends are always in the game) or runtime thing for any player? The former is easier, take photos of them and do some editing to make them line up (the 4 point cloning tool in Corel Painter is awesome for making photos fit over face textures). If it's real time, that's harder.
Facegen is a tool that can generate 3d textured head models from photos. There's an sdk so you can add it to your app. But it costs. They charge $995 just for permission to include a mesh it generated in your app, plus more for the tools themselves.