Just tiled... I was reading over on this page:
http://www.palib.info/wiki/doku.php?id=day5This part:
What happens when a background gets off the screen ? Depending on it’s size, it will wrap around or not... If your background is 256 wide, it’ll wrap around horizontally... If it’s between 256 and 512, it will not, though, because the DS default sizes are 256 or 512 large (using more selects a different scrolling mode, you can have more than 512 and it’ll wrap around nicely). When it doesn’t wrap around, it actually displays a few blank spaces until it falls back onto the background. Same thing vertically, it all depends on your background size...