Is is possible for slickr flickr to display images that are set to private on flickr that I own and then I can create a password protected page on my wordpress site
Yes, in the Slickr Flickr Pro Edition
Slickr Flickr Standard Edition only operates with publicly accessible photos as it uses a Flickr RSS feed or Flickr API call with a public connection to Flickr.
To access private photos requires the user to enter both a Flickr API key and a secret key in order to create a Flickr Signature which is used to sign the request.
This was implemented in Slickr Flickr Pro Version 1.33 which was releasedon August 25th 2011.