• Beta testing for an embedded upload service for you to upload images directly to the server via a web page
• To set this up, you might to unblock your chosen port for the web server. It would be similar to how you setup plugins like dynmap or bluemap.
• To use this feature in-game, type upload in places where you need to provide a url.

If you do not want to use this feature, make sure to edit the config as follows after you update.

#ImageFrame's convenient upload system where you can upload directly through an embedded web server
UploadService:
  #Changing this value requires a restart
  Enabled: false