I've personally never made a DTV map, but it's a bit more technical than just making shit pretty. Also, if you want your map to be added to the servers (they only allow certain ones) you're going to need to make an a.i mesh (to give bots a guide they can't screw up) and a.i barriers (to stop them from falling off ledges or even from going into the water) and even player barriers (to ensure players don't exploit your map by using ladders to reach places inaccessible to bots). The map may "work" but it's bound to have issues specifically concerning bots. Try and find some tutorials and read up on those.
Some aesthetic tips though, use different textures on certain terrain so it doesn't look so plain. You could use the path texture from the bridges to the fort, for example. Or change the wall textures of the areas you have that look like hills/mountains into something more rocky, or pebbles under the water instead of grass....And add some tree variety...they're all exactly the same.
