There are a three basic types of level layouts for CTF with their advantages and disadvantages that I have observed. These observations can be used as a reminder when level making, just what sort of game play you are looking for.
They are as follows:
Rectangular: Linear maps with usually with a base area for each team and a middle area connecting them
Levels: Gasoline powered, mentalspace, hydro, camping world
advantages: Positions on filed are apparent with attacker defender and roamer clearly stated. Fastest way to base is also apparent, while any detour leads to health ect. Great for new players. Stalemates are easily resolved due to no real hiding place for flag carrier unless defense is high.
disadvantages: Very easy to defend which results in camping, often making predictable game play
S Shaped: A non linear map with a few detours and alternative separated routs to base. Imo the best level design, offers best both worlds.
Levels: dm_castle, Dance
advantages: Camping doesn't offer full defense so more offensive strategies must be used, making it much more fun. Positions are still apparent, making team organization easy
disadvantages: Harder for new players due to slow speeds to base making it less fun. Once laser walling is discovered this is resolved
Ant farm: Many different paths to base often tunnel like
Levels: Mickctf, moonstone
advantages: interesting game play, making confrontation with the enemy less frequent, bringing the game back to ctf. Deference is a little harder unless spawn points are in base.
disadvantages: Carrier is easily hidden. Often results in a stalemate which slows game play. Players have to work all positions on the field to be successful. Game becomes very "chase to flag carrier through the pipe"