Focus on this artwork and explain the Symbolism.
Hockney drew on both the Arnolfini Portrait by Jan van Eyck and A Rake's Progress by William Hogarth in the symbolism and composition of the painting.  A copy of a Hockney etching, showing his own interpretation of A Rake's Progress (1961–63), is on the wall behind Birtwell.  
The positions of the two figures are reversed from the Arnolfini Portrait, with the implication that Birtwell is the assertive partner.  Hockney's portrait, with the bride standing and the groom sitting, also reverses the convention of traditional wedding portraiture, such as Mr and Mrs Andrews by Thomas Gainsborough.  The lilies next to Birtwell, a symbol of female purity, are also associated with depictions of the Annunciation (at the time of the portrait Birtwell was pregnant).  The cat "Percy" (slang for penis) sits erect on Clark's crotch.  The cat is a symbol of infidelity and envy, echoing the dog (a symbol of fidelity) in the Arnolfini Portrait.  In this case, Clark continued to have affairs with men and women, which contributed to the breakdown of the marriage in 1974: Hockney's depiction of the couple together but separated foreshadows their divorce.  
The informal interior scene littered with symbolic objects echoes Victorian paintings, such as William Holman Hunt's The Awakening Conscience.
Arnolfini Portrait Annunciation A Rake's Progress William Holman Hunt Mr and Mrs Andrews The Awakening Conscience Jan van Eyck Thomas Gainsborough William Hogarth