I still can't wrap my head around why, if the folder containing the relevant items but missing from the preference panes in System Preferences exists, it can't be simply (copied, if necessary, and then) dragged and dropped into the preference panes folder ... rather than the circuitous and ponderous route(s) so far suggested.
The "folder containing the relevant items" - /Library/Desktop Pictures - has nothing to do with jaybass's problem which is that
the pref pane that accesses that folder's contents is missing from his System Prefs GUI. (Whether or not it still lives on his Mac hasn't been established.)
Edit: The definitely ponderous but in no way circuitous routes, nuke & pave included, that have been suggested so far are the only ones of which I'm aware that can be used to restore the missing whatever's missing.
