(setq save-as-active nil)
(let* ((image (find-image (list '(:type xpm :file "s1.xpm"))))
       (image-dis (find-image (list '(:type xpm :file "s1.dis.xpm"))))
       (images (vector image image image-dis image-dis)))
       (define-key-after tool-bar-map [save-icon]
	`(menu-item "Save As" '("Save as" (nil) . save-i) :image ,images
		    :enable save-as-active)))
(let* ((image (find-image (list '(:type png :file "s1.png"))))
       (image-dis (find-image (list '(:type png :file "s1.dis.png"))))
       (images (vector image image image-dis image-dis)))
       (define-key-after tool-bar-map [save-icon-2]
	`(menu-item "Save As x" '("Save as" (nil) . save-i) :image ,images
		    :enable save-as-active)))

;; at this point, only the png "disabled" icon is displayed, but not  
the xpm one.

(setq save-as-active t)




In GNU Emacs 22.0.50.1 (powerpc-apple-darwin7.9.0)
of 2006-04-14 on rodrigues.inf.ed.ac.uk
X server distributor `Apple Computers', version 10.4.6
configured using `configure '--without-x' '--prefix=/usr/local''

Important settings:
   value of $LC_ALL: nil
   value of $LC_COLLATE: nil
   value of $LC_CTYPE: nil
   value of $LC_MESSAGES: nil
   value of $LC_MONETARY: nil
   value of $LC_NUMERIC: nil
   value of $LC_TIME: nil
   value of $LANG: nil
   locale-coding-system: iso-8859-1
   default-enable-multibyte-characters: t