Keep any egg shells you use when cooking, and wash them well under running water.
Fill a container with water and add any food colour of your choice.
Put the egg shells in the coloured water, and leave for around 24 hours.
Allow to dry on absorbent or tissue paper.
Repeat with any other food colour of your choice.
Allow to dry completely.
Print or draw an outline of the picture to be mosaiced.
Break egg shells into small pieces.
Put some glue on the area to be covered, and decorate according to taste and creativity.
Repeat for all the other areas, using coloured egg shells as need be.