iip-image-server-uri

... is the adress where you can reach the IIPImage server webapp. It has to be something with /fcgi-bin/iipsrv.fcgi at the end, i.e. http://wisski.com/fcgi-bin/iipsrv.fcgi or http://localhost/fcgi-bin/iipsrv.fcgi. Ensure, that it's at same domain as your Drupal instance to avoid cross origin failures.