There are three problems:
 1) The fvwm2 port uses many of the same file names as the fvwm port
    but installs itself without first checking to see if fvwm is
    installed.
 2) The fvwm2 port installs its icon xpm files in the directory
    "/usr/X11R6/share/fvwm2/pixmaps" but does not include this directory
    in its default "ImagePath".
 3) If you attempt to deinstall the fvwm2 port, it reports that it is
    unable to remote the /usr/X11R6/libexec/fvwm directory and suggests
    that this may be due to a faulty packing list.  The fvwm port has
    the same problem.

Fix: 

1) Ideally, fvwm2 should install itself in a set of file names and
     directories different from those used by fvwm.  Otherwise fvwm2
     should refuse to install itself if fvwm is installed.  (And fvwm
     should refuse to install itself if fvwm2 is installed.)
     Workaround: none.

  2) Place /usr/X11R6/share/fvwm2/pixmap in the default image path.
     Workaround: add the line:
	ImagePath    +:/usr/X11R6/share/fvwm2/pixmaps
     to your .fvwm2rc configuration file.

  3) I don't know the cause of the deinstall problem.
     Workaround: manually delete all vestiges of fvwm from /usr/X11R6.
How-To-Repeat: 
  1) Install fvwm.  Then install fvwm2 and observe that when you try to
     run fvwm or display an fvwm man page you get fvwm2.

  2) When running fvwm2, observe that (iconified) xterm icons have labels
     but no bitmap images.

  3) Attempt to deinstall fvwm2 and fvwm.