Is there equivalent directories to shared documents, shared pictures etc present in Windows NT 5.1 and later in kubuntu. These folders contain data public to all users.
If how can I tell the desktop environment about which directories I use.
The folders under /usr/share are used for this purpose. Though most are application-specific, you'll find directories for things like fonts, man-pages, documentation (for packages), dictionaries, icons, sounds and backgrounds. The drawback is that while somethings are collected in one directory (like /usr/share/icons and /usr/share/fonts), other things are spread over many... E.g. you'll find desktop-backgrounds spread between several /usr/share/* -folders, as each WindowManager/DesktopEnviroment install their own in their own directories under /usr/share (e.g. a background-folder somewhere under/usr/share/kde for KDE).