Artists can create a sense of motion in their mosaics by using concentric curved rows of tile, especially in the background around figures.
To me this use of andamento* is one of the most interesting aspects of mosaic, and it is an easy way for novices to make art that really engages the eye. I used this technique in the first mosaic I ever made, and when I used a photo of that mosaic to make our logo, I blacked out the figure of the fire bird to emphasize how much of the sense of motion was creation was created by the andamento in the background.
*The Joy of Shards mosaic website defines andamento as the visual flow and direction within a mosaic produced by the placement of rows of tesserae (pieces of tile).