So I hooked up a small setup of Map Generation in Azura and got the following render.
Notice the black lines? I think these black lines are due to the floating point values assigned as the texture coordinates. As only the texture map has black backgrounds.
If I move the map somehow the lines change. This may be because the camera has a tilted view towards some of the tiles causing them to be rendered this way? Here is another screenshot of the camera moved a bit to the left:
Notice how the black lines are now at the center? .. Weird … Investigation going on!