Forum OpenACS Q&A: Where to store and retrieve ad hoc images

I have a package that queries for a set of map coordinates, renders them using a package called Generic Mapping Tool (GMT), and eventually displays an image in a web page along with the text-based data. Yes, it is a scary kludge when you do a lot of work to generate a postscript file then turn around and turn it into a PNG. For frequent requests, I'd like to cache the image. Where's an appropriate place in the file system for this sort of thing? Is there a way to tell the request processor to "look here" so to speak? Since this package can be installed multiple times, I need a namespace that won't collide on different package ids.

I am open to other workable alternatives to GMT if you've got any suggestions. It was never designed for this sort of application.