A displaying device comprises a movable storage device adjustable between at least a closed position and an open position, an elastic image-building body adjustable between at least an inactive position and an active position. The image-building body, in its inactive position, is arranged to be accommodated by the storage device in the closed position thereof. The image-building body includes a substantially gas-tight cavity. The displaying device includes a valve arranged to be connected to a gas source, the valve being arranged to provide gas communication between the gas source and the cavity, so that the cavity may be filled with gas, and the image-building body may be raised into its active position when the storage device is in its open position. A method is for using a displaying device. A compressor is for putting up an image-building wall.