Achtung Baby was an attempt to challenge what listeners thought they understood about U2. The style of music changed as they shifted from the heavier, monochromatic style that they had used in their previous few albums towards more EDM and techno styles that were becoming more popular during that period.
The album cover also reflected this shift as they no longer used a single picture but instead featured a mosaic of 16 images. Possibly also reflecting U2’s choice to change and the new possibilities there could be.