Edit: I thought about it a little, and the XML output could be awesome! If you look beyond just images, it's possible to quite easily make an mp3 player that plays all the files in the directory (in the browser), RSS feeds for the newest files, and more or less whatever.
Edit again: Static file caching anyone? It shouldn't be too hard to implement it, just compare the last edited date of the saved XML file with the created/last edited date of the latest file in the directory. If the XML file is newer than the other file, return the the saved XML file. Otherwise just (re)generate it. It isn't needed or even possible in all situations, but hey, it could become a nice plugin.
One last thing before I fall asleep. If you strip out all of the XHTML rendering from GIS, and maybe make comments, counters and uploads separate plugins, wouldn't GIS become, like, really small?






