image made from an assemblage of small pieces of colored glass, stone, or other materials / From Wikipedia, the free encyclopedia

Mosaic is the art of decorating a surface with pictures and patterns made of little pieces of stone, glass or tiles of different colours.

The most famous mosaic of Ancient times is in Pompeii and shows Alexander the Great
An early Christian mosaic in Rome

Mosaics can be used indoors on walls, floors and ceilings. Mosaics are sometimes used outdoors on pavements.