I've used CTF mode to build a map where the flag and return/capture both for both teams are completely dynamic. That is, they move every time a flag is captured, by team. The clan loved it. Very fast paced, prevented deadlocks, and kept people moving and thinking.
The biggest variable I've found with CTF is where you place the flag and capture points relative to the bases. This may seem obvious, but there really isn't any reason why the red/blu bases have to be involved in any way with the flag or the capture point.
Moreover, you can also have a common flag and a common capture point, in another variation.
Put simply, you could have something like this:
.\C/.
R X B
./F\.
if you get what I mean, where red and blu teams spawn in arbitrary locations as long as both are equidistant from both the flag and the capture point. This keeps the action away from the bases and out in the field. Solves a lot of spawn-zerging problems without having to make the respawn time overly long, which many (if public servers are any indications) players dislike.
How about a city/town theme where the flag & capture point each spawn in different buildings each time, and there are no bases? Wrap your head around that one... :laugh:
Additionally, there are also mechanisms whereby a/the flag(s) are kept out in the open, but to gain access your team must perform a task, reach a goal, obtain a key, do whatever. This adds another dynamic.
Finally, you can mix it all up with having to grab the flag at YOUR base and take it to the heart of the other teams territory/base to score. And to really make it hard? Return time of zero on the flag, that's always a curve ball.
Custom CTF is all we play on our private server. Our clan didn't want custom CP/PL as there's so many of them in Valve's official map list already. :thumbup: