It is always hard to keep the heart of a project intact during the development process. A lot can happen in-between. What it has not to happen though is completely change the core of it.
It does not mean you write on stone what you do in the pre-production phase and nobody have to change it. On the contrary: the final result is a team effort made of listening, creation and improving, respecting of each professionalism involved. But if you can communicate your beliefs powerfully on your visuals at the beginning, the rest will follow.
During my time as a Creative Director for Team Park Project, I did a mood sketch as a base for the later development. The final result in photos looks quite similar, even though the elements involved have changed during the process.