Minecraft-Overviewer can be used to render Minecrat's maps and make them navigable in a browser using Google Maps API, so my python script actually works on any Google Maps image chunks.
To use it, just type in a terminal:
./mergeMap.py <blahblah/ZoomN> <output.ext>Where "ext" can be any format supported by Python's PIL library (so PNG & JPG for sure).
With Zoom > 4 the processing time / disk space required / RAM required could easily become a problem and the OS could freeze ;)
Screenshot: Zoom6.jpg Zoom5.jpg
(Sorry, no thumbinals... they are HUGE images :D something like 10K x 10K and 20K x 20K pixels)