I modified the 8x8 tiles and the map16 a bit. Now, the back area color is separated from the actual tiles, so you can use a layer 3 background with it. I've also included a .mwl file with a version that scrolls horizontally.
I really like this background actually. Other than the tiles being a bit jumbled because it's a rip and usually people just insert and use BG rips as is, it's pretty easy to build new arrangements and castle structures with.