I've updated the repo and the files section with another new map, map3.csv. There is also a small tweak to the main code py to guard against the player moving off the edge of the map if there isn't a wall there.
In building the new map I did run up against a MemoryError when trying to load the map. map3.csv is about as big as maps can be right now give or take a few rows or columns before it gets to be too much and throws the error during loading the map.
I think we can make the map loading and storage a bit more memory friendly by assigning number IDs to each tile type and then using a dictionary to look them up. I'll probably explore this avenue and if it's fruitful add it as an update to the main CSV Tilemap Game project.