There are many illustrations available - cigarette cards, programmes, theatre posters and prints - as well as books and on the internet..
This is an example of the Player's Cigarette card series
The first night programmes often have interesting pictures and also contain the names of the actors who first played the parts
Theatre posters depicting characters in the operetta
The wonderful series of watercolours produced by Flint - here we see Gamma sneering at the ladies of Hildebrand's court.