The AM stone is engraved on all sides.  But for now, let's take a peek at Side "A".  

There is quite a handful of info here -- so much, I'm not even going to try and point it all out.  For now we'll look at several different images of the same side, as different lighting (and yes -- imaging) reveals more.

Let's first take notice at this figure located in the upper center of the stone.  The image below primarily shows the head of what appears to be a spirit being. 

Note the shape of the head.  And the possible ears, or horns, whatever.

I believe that the entire stone itself was modified into an effigy.  Possibly an effigy of the figurehead below.