If the rest of the mask is now not displayed, then the edges of your image cannot be black, otherwise you wouldn't be able to see them. If you can, post a link to your image and we'll take a look at it.
As for SetScale affecting TileImage, I'm afraid it does not. SetRotation doesn't affect TileImage either.
As for SetScale affecting TileImage, I'm afraid it does not. SetRotation doesn't affect TileImage either.