Figuring out all the details too early in the design process can be deadly. It forces unnecessary decision making and is a huge waste of time. Far better is to show something that you know is possible but might not work exactly the way you are showing it. This gets you past the first hurdle: approval and feedback. Then you can go figure out the next level of detail and recalibrate. In the end what you had in mind in the beginning will look different from what you have in the end but you will have retained its essence.