Yes!! So I set up an Apache Web Server and hosted the cell images and map image as-is and everything is back. The key for me was the WorldMapImage.jpg file in my steam cache was a 404 html response, not an actual image.
So the login map preview in ServerGrid.json is MapImageUrl and the server grid files (cells and mapimg) is the MetaWorldURL, which is only a directory path on the web server.