Removal of non-free files from repository

Hi, all Please refer to this Debian bug: https://bugs.debian.org/771191 It has been noted that the Lena image we distribute (even though we no longer use it ourselves anywhere) is not fully free. In other words, Debian would be forced to release a version of scikit-image without it. I thought we could make their lives easier by simply removing the image from the main repository. What do you think? One question is whether we also remove ``data.lena``, or change it to return astronaut. Stéfan