This is almost what you want (but surprisingly far from it):
t := OpenThemeData(Handle, 'STARTPANEL');
DrawThemeBackground(t, Canvas.Handle, SPP_USERPICTURE, 0, rect(10, 10, 100, 100), nil);
(Delphi code, but only WinAPI functions.)
, - : http://msdn.microsoft.com/en-us/library/bb773210(VS.85).aspx