Mike Gleason has created two very nice examples of zoomable images created with the Google Maps API. He has also written a step-by-step tutorial explaining how you can create your very own image maps.
To help you create your own map tiles from any image you can use Mike's C# Code - Tiles Generator (a guide on how to install and run the tile generator are included in the tutorial).
The two example image maps include a simple zoomable image of Lara Croft and a more interactive image map with custom controls.
The custom controls in the 'Earth' map include hand drawn looking zoom buttons and some hand drawn buttons which open information windows on the map. The information windows themselves continue the hand drawn theme.
Create Zoomable Images Using The Google Maps API