how to: additional icons

[Didier Wiroth]

Hey,
(I'm using xfce4 on FreeBSD4.7)

I have installed evolution & openoffice and I would like to add buttons, 
with evolution or openoffice specific icons to the taskbar.

1) What format do the icons have to be?
2) Can I download additional third party application icons for xfce4 
somewhere?
3) Are there specific icons requirements for xfce4 (format of the file, 
different sizes etc..)

Thanks a lot!
Didier