The most simple macro is a macro which does not accept any arguments. You might define the location of the company logo within a zero argument macro.
<al-macro name="small-logo"> <img src="http://images.company.com/logo/small.png"> </al-macro>
Then whenever you need to display the logo all you need to do is expand the macro.
<al-expand name="small-logo"/>
This allows you to define the location and name of your company logo in one place.