Can I suggest the following patch that allows the use of labels under  
the icons as is standard on the OS?


2008-04-05  David Reitter <david.reitter@gmail.com>

	* tool-bar.el (tool-bar-local-item): Accept string for KEY
	as icon label.
	(tool-bar-setup): Use readable strings for labels.
	

2008-04-05  David Reitter <david.reitter@gmail.com>

	* macterm.c [USE_MAC_TOOLBAR]: Add Vmac_tool_bar_display_mode.
	(update_frame_tool_bar) [USE_MAC_TOOLBAR]: set display mode.