As of Beta 0.40, Ace Of Spades had a map editor tool and the ability to save a map from in-game (using the F1 key).
This led to the creation of custom maps, from trench warfare to urban assault it could all be made in the map editor.
More tools and information for making your own custom maps can be found here on the Ace of Spades forums 
 Play a custom map
Custom maps cannot currently be loaded from the game itself. It must be included as part of server setup.
Upon loading 'server.exe', a message appears saying: "Type 'gen' to generate a map or mapname to load a map (exclude .vxl extenstion)". Here, enter the name of your saved map.
Note: Your map must be stored in the 'vxl' folder of your Ace Of Spades directory in order for it to load. Also, the map name cannot contain an underscore.
If your server and port forwarding are setup properly, you should be able to see your server listed in the browser. If not, follow the steps on the server hosting page.
 List of Released Custom Maps
Note: Here are many other custom maps.
Note: Edited to include archive links where available. Links on the archived pages may still work.