To post screens upload the pictures to places like
Image Shack. Then tag the pictures onto the forum using the forum link that Image Shack provides. More info on how to post pictures in your posts can be found in the FAQ section of this forum.
Edit: Luckily enough for you, when I'm bored I become a rather nice helpful person, here's some screens of your map like you asked. Personally I don't think it's that bad for your first map, though your scenery placement needs work. Also, I don't understand why you made it so big if all you put on the ends is bonuses spawn points.
Gameplay seems like it would either end quick, or take forever because there's only one route for people to capture the flag.
Anyways, good job for your first time.
Screeny Linkage-
Ctf_The Trench War