Answer:
They are called mosaics.
Explanation:
A mosaic is a kind of art in which the artist has to put together small pieces of different materials in order to show an image, the most common materials for this kind of technique are colored glass or stones.
Given the fact that sometimes pebbles are used, they receive the name of "pebble mosaics".
It is common to see this kind of art in religious places; however, It is also very likely to be used in interior decoration in general.
