I'm not sure if anyone mentioned this, but I recently tried 'Leafletjs' for the exact purposes you are describing.

It is open source, has lots of simple plugins, can be set up on your server in minutes, and best of all, accepts image layers. So you don't have to 'chop up' your image using a slicing script. You can also set your own coordinate plane. So you can really create your 'own' world map.

Here is a link:

http://leafletjs.com/