Maybe sheds based on or inspired by different things in the game? Some of the theater movies have interesting imagery. The world of Wumbus and Bobo. Some of the paintings suggest unusual locations that we don't get to see, like the purple one that is called Night Vision or something, and the yellow and orange desert one, and the one that looks like a Mediterranean villa.
You could probably make something Wizard of Oz, or Studio Ghibli. I see you've made indoor water, could you make a waterfall?