I've been looking at the source of the world map page through Chrome.
Could you check blog.shatteredkingdoms.org/tiles and verify that you have the following .png files:
2_4_0.png through 2_4_6.png?  
Code:
 lines 229 - 244
  // tile range in one direction range is dependent on zoom level
  // 0 = 1 tile, 1 = 2 tiles, 2 = 4 tiles, 3 = 8 tiles, etc
  var tileRange = 1 << zoom;
  // don't repeat across y-axis (vertically)
  if (y < 0 || y >= tileRange) {
    return null;
  }
  // repeat across x-axis
  if (x < 0 || x >= tileRange) {
    x = (x % tileRange + tileRange) % tileRange;
  }
  return {x: x, y: y};
}
In the first comment section of your code, it states that a zoom of 2 (which is as far out as we can zoom) the number of tiles is four.  When we look at the available .png files it does not have 2_4_0.png. 
So based on my findings, it appears as though any .png files from an x coordinate greater than 3 (while at zoom level 2) is missing.
I also think the issue could reside within the   // repeat across x-axis section of the code.  Since the image repeats, it isn't allowing these 2_4 png files to load in. I tried making a local copy of the page and changing the x if statement to work like the y if statement, but the map still wrapped. 
Could you at least check for the missing png files?