How do I change the path to the upload folder used by Community for Image and Document archives?
This is done by changing the default settings in the configuration files for ImageGallery and DocumentArchive. This is explained in detail in the document "Installation Instruction EPiServer Community 3.1" (or if you are using an earlier version "Installation Instructions EPiServer Community 3.0"), you can find them here.
Generally each module have its own .config file that is located in the module's folder. For example you can find the ImageGallery.config in "[your_web_roor]\Netstar\StarCommunity\Modules\ImageGallery". In this file you have several different settings, for instance "ImageAbsoluteFilePath"and "ThumbnailVirtualFilePath".