Complex sentence: Sickert was a cosmopolitan and eccentric who often favoured ordinary people and urban scenes as his subjects, but whose oeuvre also included portraits of well known personalities and friends, as well as images derived from press photographs.
Split into simpler sentences: Sickert was a cosmopolitan and eccentric who often favoured ordinary people and urban scenes as his subjects. His oeuvre also included portraits of well-known personalities and images derived from press photographs.