The above are just a few. I'm sure all the photos on these sites are copyright protected, but you may view them.
I still question why you want to have nude photos. I was not suggesting that you ask a student in India to pose nude, but that you, or a male student could wear the traditional lingoti (sp?) to photograph the asanas. I do wonder a little why you're asking for such photographs from elsewhere, especially when so many wonderful books and photographs exist already.