I'd like to know, if there is any way to replace the default button of <b:commandButton> with a <b:iconAwesome>.

However, it does work with a <h:commandLink>, perfectly.

<h:commandLink>
    <b:iconAwesome name="arrow-down"></b:iconAwesome>
</h:commandLink>

And with replacing, I mean fully replaced and not, that the icon is on the button. Just check the working code above.

Are there other hints to be mentioned?

(Note: <b:...> is a component of BootsFaces.)