Jack Child, American University, explains the history behind the icon we use for MACLAS:

When we prepared the first MACLAS Newsletter (I think it was in 1979) we were looking for a distinctive and attractive icon relating to Latin America.  We decided on the central figure of the gate at Tiwanaku, Bolivia.
I visited the site a couple of times and was impressed by it. The stone is now worn, and what we used was redrawn.

Here is a postage stamp with the icon, from his 2008 Duke book, Miniature Messages: the Semiotics and Politics of Latin American Postage Stamps