If you want to remap one of the original backgrounds, this is a short tutorial on how to do it.
First please check if this is even neccessary for you to do. This is only for those who have been assigned map16 tiles above page 50 and who want to use their map16 tiles with one of the original game's backgrounds. If any of this applies to you, please follow the steps below.
1. Copy the original background tiles from pages 40 and 41 to pages 5E and 5F
2. Click on "Level" and then on "Remap Background Tiles.." as pictured below.
3. In the new window that pops up enter "+1E00" in the upper text area as pictured below.
4. Click ok and you should have successfuly remapped the original games background to the new pages. You can now add your own tiles from your map16 tiles and edit the background using the tiles on page 5E and 5F.
If you have any questions I'm happy to help!