I have a good idea how it is possible to decorate a ceiling. For this purpose it is necessary to create the special monitor at the ceiling or even a projector which would show various stages on the ceiling. It would be possible to use an aquarium as a plot in these stages as it was mentioned earlier, or the star sky, space, sea depths, etc. It will be some kind of screen-saver for a ceiling .
The same thing could be designed for walls or even for a floor. It will be cool. Imagine, you're walking on the water, or you're walking somewhere in space or in clouds. In general, it's all limited only by your imagination. Though projector can't be used for a floor as your shadow will mar all show .