In Netscape do Option Menu, Preferences, Helper Applications.
Do "New..." and set the "Mime type:" to image and the "Subtype:" to rotater and "Extensions:" to rot and "Action:" to Launch Application and use the "Browse..." button to select the copy of Rotater on your machine. The "File type:" should be TEXT.
In other web clients do the equivalent with the Mime type image/rotater and the extension rot.
Now you should be able to click on the images and have Rotater automatically start up and show them once they are downloaded.
If you want to keep local copies of the files you will probably need to grab them from the temp folder before quitting your web client or they may get deleted.