The following activity is illegal on Facebook and could result in your page being permanently deleted by Facebook;
A promotion that requires a user to;
- tag themselves in the photo.
- to change their status in any way
- to change their profile picture
- to answer a question in a status update
- any kind of response in the status
- like a photo or an update
- add friends
- respond with a photo not in a specific application
All promotions need to run through an application that does not use any of the basic functionality of Facebook.
However, I have not heard of any Brand Pages being deleted for this type of activity. I am not game enough to take any chances though.