 Complete the following phrase:  The work is a tempera or egg-based painting on a circular wooden panel or tondo with a diameter of . It depicts the Imperial family wearing sumptuous ceremonial garments. Septimius Severus and his sons are also holding sceptres and wearing gold wreaths decorated with precious stones. This image of a grey-haired Severus, with his wife and young children, emphasises the dynastic ambitions of the new emperor after the turbulent 