Change a background tiles image on the fly

I have been poking around for most of the day trying to figure out how to change a background image on the fly.

Basically what I have done was create a fxTileMap2D object that is 16x16 tiles in area. What I need to do is have a mouse selected tile change it's image.

Here is the code I am messing with:

function CreateTileMap() { 
   //Create tile-map.
   $playMap =new fxTileMap2D(){scenegraph =t2dSceneGraph;};

   //Load saved tile-map file.
   $playMap.loadTileMap("~/client/maps/dungeon.map");

  ...removed for brevaty
}

// select the tile under mouse
function sceneWindow2D::onMouseDown( %this, %mod, %worldPos, %mouseClicks ){

   // get tile layer (works)
   %id = $playMap.getTileLayer(0);

  // get x,y loc of selected tile (works)
   %xy = %id.pickTile(%worldPos);

   // change tile at selected locations image
   


   echo(%xy SPC %id.getTileType(%xy));
}

My real problem is that I can't seem to figure out how to grab a pointer to the tile object itself, and/or utilize the setImageMap() command to swap the image tile.

Can anyone point me in the right direction?

Thanks in advance!
-Jeff