Temporary Veneers should look similar in shape size and alignment. Your smile is often undergoing a dramatic change when you have veneers placed. As a consequence pre-planning is critical. A wax up which acts a template is a great way to plan out you case. This model is what I use to make temporaries. Some Dentists will not do this step and use your existing teeth as the template. Although that is faster and less costly way of practicing, the problem with that method is that you do not get to "try-out" your new smile.
Wax-ups clear up a lot of issues such as size, shape, length and alignment. If you do not like these temporaries, you will not love your smile. Any issues need to be cleared up at this stage. Once you are happy with the temporaries, then we take pictures and models to send to lab, often sending the patient to lab as well. Our goal is to mimic this new smile.
Keep in mind I did not mention the "feel" of temporaries. Many patients mention the plastic, artificial feel of temporaries. Modern science has not solved this problem yet. In addition, color with plastic temporaries is never the same as porcelain, they are just too different. That said, veneers are fabulous and the temporaries should start you towards feeling great.