You'll need:

• the group photo from the year before to put on the website

• a skyline of the host city in vector form to be used as a base for other artwork pieces
• an avatar format icon to use on twitter, most likely derived from the above skyline
• attendee materials
  • badges for blogs ("I am attending GUADEC" and "I am talking at GUADEC")

  • presentation themes

  • Posters for outreach at e.g. universities
  • posters to put up at social events and venues
  • banners to go on stage, with sponsor logos on them (which sponsorship logos go on the banners should be detailed in the sponsorship brochure)
• general signs with room names, arrows to give directions, price lists for merchandise, and so on

A large collection of designs was created for GUADEC 2017. It is recommended to reuse them!