Large-format tiles can create a sleek, modern look, but they may not be the best choice for the shower floor. Smaller tiles, such as mosaic or smaller squares, are typically more suitable because they provide better traction on the sloped surface of the shower floor. Larger tiles may not conform to the slope as well, increasing the risk of water pooling and making the surface slippery. It's advisable to consult with a professional to determine the right tile size for your specific shower design.