Custom Icons in Toolbar

I created a bunch of macros to insert "smiles" into messages I am
composing. I then created a toolbar, and added the macros to toolbar
buttons so I just have to click on the toolbar button to inser my
Smilie.

What I would like to do is substitute the text labels in my toolbar
that say "Smile", "Frown", "Sad", "Cry", "Headbang" etc, and replace
it with the actual smilie.

How do I do this? IOW, How can I replace text on the toolbar with my
own home-made icons. (I can resize the smilies for use in the toolbar
if necessary).

Thanks.

-WVmontani