I have the same problem on putting a 70x70 tiled-background and shows the white spaces in-between the map in the tiled-background layout view. So the solution is to change this 70x70 pixel resolution map to 64x64 pixel and walla...all fixed! apparently all mapping should be in 32x32, 64x64, 256x256 ratio or higher. I'm a newbie (obviously), so need to read more things in the forums...