use sc save instead of save in the map editor. This will create a file per layer. For each layer, load that as a dat: file into an array then pass that array to bgload. If you have custom tiles load that as grp5:filename.
Here is a demo of what I mean. You can skip the grp5 load if you don't have custom bg tiles. While you still want to save in the map editor so you can edit things. The layer files you get from the sc save command. Change the file names as appropriate.
You probably want to change 64, 32 to 64, 64 in the code since I was only using the top half of the map. If you do it right you can get something like the attached image. Truthfully however, I might just skip the map editor and use read/data commands to design things since you can't choose any size other than 64x64 in the map editor.
That is just one map, but it has four layers. If you put everything on a single layer, you can skip the other three. For multiple layered maps, you can move the layers at different rates to get a nice parallax effect.