Pong mode is pretty simple to set up -- it's just like 1flag ctf except you use a gamemode of 64, so add that gamemode to your bases and a "flag" entity in the middle of the map with gamemode 64, and you're good.
Some things you might want to tweak:
- Don't really like the flag placement. It looks way too easy to defend, plus the flags aren't in a very obvious place. I was running around on the map for a few minutes before I even noticed they were there. Thought I had the map loaded in the wrong game mode. Once you grab the flag, you're forced to trudge through the water, under the bridge, and up one of two small exits, both of which would be very easy to defend. Unless there's nobody at the base defending, I imagine getting out of there alive would be very difficult (without having to eliminate all of the defense). I think it would be a lot more straightforward to just put the flags on the bridge.
- The walls next to the bridge are kind of annoying as they force you to trek completely to the other side of the hill (as mentioned above). I'd leave just enough room to squeeze through them.
- The walls need to be a bit higher. There are a number of areas in the map where you can see over the walls and you can see random pieces or other parts of the map (you can see part of the blue arch in your second shot). Looks like weird artifacts -- something you'd want to avoid.
- Texturing is inconsistent. Some areas have dirt on the slopes and grass on the top. Others have dirt on the top with grass on the slopes (looks weird). The blue base has a large area of dirt which is grass in the red base. The posts for the red bridge are made out of the rock wall texture instead of stone like the blue bridge.
- If you're going to have a center flag, you need to make it more accessible (I assume that's just where you're planning to put the pong ball?).
- Lots of little areas that it seems like you should be able to fit through but just aren't quite big enough (stuff like that is annoying in the heat of battle -- should be a quick fix with a couple clipping planes, though).
I can put together a demo to point some of those things out if you want. I've uploaded the map to the beta server for testing (you remember the login pass?).