Puzzle Frenzy was built on top of a previous app I wrote for WP7. At that time the app was more simple and the gameplay more limited. The images used, the pieces shape and the difficulty levels were different as well.
For Puzzle Frenzy one of the first things I changed was the puzzle pieces shape.
A great deal of attention was dedicated into making them as familiar to the user as possible.
The WP7 app was using a simple rectangle and four ellipses as connectors for drawing puzzle pieces.
Now I use a Bézier curve with 10 control points for each edge of the piece.
Therefore each Puzzle Frenzy piece is a Bézier curve with 40 control points.