A mood image is the visual presentation of a mood. These images are used in creative professions from film to interior design to convey an idea of the emotional atmosphere of a physical space. Composites of mood images, giving the idea of similar moods, are sometimes known as mood boards.
A mood image or mood board is generally used when the mood is fairly complex and difficult to grasp. There would be little point in creating such an image if the mood in question were simply "happy" or "gloomy." Tennessee Williams's play Twenty-seven Wagons Full of Cotton has just such a complex atmosphere, and it is worth trying to describe this before thinking of images that might convey it.
The play concerns deceit and duplicity between three people, none of whom are portrayed in a sympathetic or positive light. Jake and Flora's marriage appears cloyingly sentimental, but the superficial sweetness of Jake's behavior to his wife masks an abusive relationship, in which he is more like a domineering father than a husband. Jake is able to exploit Silva, a business rival and an outsider in the small Mississippi community and Silva, well aware of this exploitation, decides to take his revenge through sex with Flora.
Williams provides a good image for the play himself in his description of Jake and Flora's home. This includes ersatz Southern gothic elements, in the pillars and stained glass, but an overall effect that is rather like a doll's house, with "fluffy white curtains gathered coquettishly in the middle by baby-blue satin bows." The idea of a doll's house expresses Flora's childishness well, but the mood image should show traces of rottenness at the edges of the house, along with the fake gothic pillars and stained glass. The effect of the image should be a house that is both fake and unstable, cheaply-built and pretentious, with window dressing which suggests an ineffective attempt to cover up its fundamental unsoundness.