This is the schematic for the wallpaper map art in the my Texas Big House build.

• Paste the schematic in a map aligned part of your world and create a map of it.
• Use the map to fill the item frames inside the Texas Big House to use as wallpaper.

This is the only way I know how to do this unfortunately. If you know of a simpler and easier way let me know.

The wallpaper uses all the same map only the bottom row is upside-down.
When pasting the schematic in your work, take notice to ensure it's aligned properly to the map edges. It's easy to get it wrong by 1 pixel which will make the wallpaper look bad. I use both litematica and wordedit when building and for me it's easiest to past the schem file in a trash world, make a litematica schematic with it and use litematica to align things much easier. But this is just my preference.