Attached is a patch to window-tool-bar. This adds support for the rest 
of the tool bar item specifiers.  I have been running with this locally 
for a couple of months to ensure it had no major performance regressions 
because it does add more code run per tool bar item refresh.

Separately, I also have an example tool bar mode that I use alongside 
developing the window-tool-bar.  This example shows off the capabilities 
of tool bars.  At the moment, it is limited to just what window-tool-bar 
supports.  I'd be happy to add that as well to Emacs for any further 
tool bar development in general.

   -- MJF