Hey, inspired by the Djakota postig I whipped up a little wrapper around IIP [1] and VIPS [2]. It is basically the same think as Djakota, but as a compiled fast-cgi program (rather than Java).
A couple of examples: http://toolserver.org/~dschwen/iip/wip.php?f=LC-39_Observation_gantry_pano.j... http://toolserver.org/~dschwen/iip/wip.php?f=Chicago.jpg http://toolserver.org/~dschwen/iip/wip.php?f=Seattle_7.jpg
The examples use a flash viewer, but you can append &flash=no to the urls to get a Javascript viewer.
It should work to replace the names with arbitrary images on commons, but new images will have to be processed into a pyramidal tiled tiff image (with jpg compression) first. That takes time, about a minute. After that the image is cached and the viewer appears immediately. Be warned, there is no visual feedback that anything is happening while the image is processed. So be patient and try a reload after waiting a minute or so.
I'll write a gadget to integrate this into commons (the gadget will only appear on images with a certain minimum size).
Best, Dschwen
[1] http://iipimage.sourceforge.net/ [2] http://www.vips.ecs.soton.ac.uk/index.php?title=VIPS