That's because Tile World 2 boxes and pictures for everything. If you look closely, you'll see that the top left of the background is lighter than the bottom right.
EDIT: I'm guessing scratchthumbs.db is used for the background. The file isn't in TW 1 and has a bunch of picture file names in it.
EDIT: I'm guessing scratchthumbs.db is used for the background. The file isn't in TW 1 and has a bunch of picture file names in it.