Great, thank you!
If and when you have time, perhaps you could also bring some consistency for other structures in the art/ files? E.g.:

• cc, civ_center, civiccentre, civic_centre, civil_centre → civic_center
• docks → dock
• theatre, theatron → theater
• defense_tower, scout_tower → tower_large
• sentry_tower, wooden_tower → tower_small

And:

• celt_wall → gaul_wall
• hele_wall → mace_wall
• siege_walls → siege_wall