One of the ways I work with clients so we understand all the parameters of a project design, is to create a maquette. A maquette is a small work-up of the project. This is generally used on sculpture projects and provides a better visual to the client. Mosaic art work has many factors, the individual tesserae, the andamento (flow & placement), and the grout color. I highly recommend creating grout color swatches so the client may choose which grout color they prefer.
These swatches all contain the same tesserae yet have different grout colors. Notice the difference the grout can make.
The client picked the white grout and I grouted the maquettes.
The maquette is generally a to-scale sculpture. These were not designed to scale, only as examples. Even so, the client has a pretty good idea of what the finished project will look like when combined with the rendering.