This project should be "weighty". That means it should be a large project that encompasses many of the skills learned in class. It also means this project should represent something the student takes pride in.
Because each student will choose something unique, a grading scale is difficult to formulate. Therefore, most of the grade will be based on use of class time and the quality of the finished product.
The above are by no means the only qualifications for Quality, but they are the main ideas to consider.
Evaluation:
10 points -- Use of class time
10 points -- Quality of finished piece
20 points total.