Do some 3D Modelling

I would like you to make 5 very nice different book case designs, subject to the following conditions: 1. Each of the designs needs to have something unique / different to the other designs. 2. Each of the designs needs to be (to some extent) customizable / configurable / extendable / scalable. A design needs to act like a concept that customers can configure themselves by adjusting size, choosing the number of shelves, the width, where to have doors, etc. So, for each design, I would like to see two different configurations. 3. The designs needs to be modern or contemporary, for European market. 4. Very IMPORTANT: we are looking for designs that can be constructed easily also. 5. The choice of the materials / finishing is not so important. We would like to choose ourselves what decorative materials we will use. What is important is the shape. 6. We prefer designs that do not use a lot of material, above designs that do so. So using thinner shelves, less doors, etc... But this is a soft constraint, since we are looking for different designs. File format: to be discussed.