@Sonkiki Do you have any more of the files for these, or know who we could ask? I see some of the files are linked here, which is great.
But it would be great to go through and try to find the rest, particularly for the ones that could be reused. E.g. there was a poster about the Friendly Space Policy. We should update that to also mention the Code of Conduct.
If possible, it would be best to request the original vector (typically SVG) files from the designer who made each file. This is the original file, e.g. from Adobe Illustrator or Inkscape. Some of them are only available as raster (JPG), e.g. File:Hackathon Vienna Invitation.jpg. This loses quality when copies are made and is difficult to edit.