Hrmm, I hadn't thought about messing with the bit-depth for palette images. I can add that into an additional round of testing. Right now the worker daemons can fork themselves, and work on multiple files. Although this is a different image per-process id. Each process has an expiration time in the event a worker disappears without ever reporting the results of work. But splitting up the work for a single image isn't out of the question. Perhaps the workers could run a combination of the two depending on the status of the work pool.
When the time comes to make a friendly windows version of the worker, the ability to go through local files could be an option. You'd just skip the logic that requests work from the server and run it through the same system calls to pngout.
There's a lot of work to be done still on the utility. But I was getting excited and wanted to do some testing
By the way, the policy right now is to keep the images on the server for a few days after they are processed. You could use this utility as it stands now to upload submissions to the site. Just give Jon the URL for the image when it's done.