Origin8 have designed many of the posters for this group and they include images that are either photo-realistic or illustrated. This example was for a production of The Happiest Days of your Life. The forerunner of the St. Trinians films. The image is based on a collection of Ronald Searle cartoons combined into a single illustration more fitting for the plot of the play.
Find more examples of show poster designs at pumphousetheatrecompany.com