If you want to review a CTF level, here are a few things you need to know about CTF:
A CTF level consists of 2 bases and 2 teams. Each team must take the opponent's flag to his own base. The opponents will shoot the flag holder down. If he dies, the flag will return to its owner's base.
In a good CTF level, there must be various paths the flag holder can take. If there's one only path, the player will be certainly shot down, and the game will go on forever.
A few advices for both battle and CTF games: There must be a variety of weapons and goodies all around. The most powerful pickups should also be the rarest and best hidden ones. In general, the ammunitions should be floating 2 or more tiles above the player. Otherwise, he can get them too easily.
All paths should be smooth enough for the player to run through them with ease. The ceiling should be tall enough to allow the player to dodge the enemy bullets.
Don't place more than 1 or 2 dead ends in your levels. In general, you shouldn't place any dead ends at all, but if you're good enough at making levels, you may place 1 or 2 in very strategical places.