It would focus on the upside down thinking of Jesus.  Principles he taught and lived by that might be considered backwards.

Example:
Love your enemies.
Lose your life to gain it.
Rejoice in your trials.
etc…

**EDIT 092308**

Apparently David A. has been doing some sermon thinking as well.  He has a series planned for January along the same lines.  Read about it here.  This will be a good opportunity to see this idea in action and possibly adapt it for the students.