The registration icons mainly consist of a grid common in all icons, while the actual purpose of the individual views is cramped into a secondary icon in the bottom-left corner of the overall icon. They are hardly distingushable from each other in the usual toolbar icon size prevanlent in the MITK Workbench.
Since the toolbars are separated by categories anyway, the secondary icons mentioned above should be the main icons, while the common grid icon could be removed to reduce visual complexity.