The map looks very empty to me, even if there're some boxes and barrels in it. But all boxes and barrels are placed in corners, where they can't really influence the gameplay. You can just run the high area along without notice them and without getting blocked by anything. Also the mid high area looks very boxy. A bit more detailing would be cool. Maybe get some inspirations by pictures.
The other things I've noticed have to do with the structure of the map.
At the moment there're two long pathes and you have to decide if you go high or low. A fast possibility to change these two pathes would be great. Not sure how to add this without changing the structure, because there's a big gap between the high path and the low path, so a ladder wouldn't work well.
Also the sky is a problem with this map. Sometimes you can hit the sky while running/jumping downward. And of course it shouldn't be possible to see other parts of the map through the sky. That looks just horrible and unreal. Probaly it's hard to fix without changing the structure here, because I guess just changing the sky to a normal texture would look bad, too.
Looking at other maps or copying parts of them could help you to improve the structure of your own maps.
Away from the structure, I like that you aligned the boxes and barrels well
Mid low is too dark.
The sun angle doesn't fit the sun and create weird shadows. Try something like "_sun_angle" "90 -30".
Add some more player spawns. Also add "angle" "#" to them that players don't look in front of a wall after spawning.
Maybe add some items like co2 or ammo.
It's hard to notice where to cap. Maybe change the base/flag entities or move the colored floor to the base corner.
I guess that's all for now.
Map is online @ [OTB] Beta!
@Rockyar_96: The new subforums helps to navigate in the mapping board a little bit better in my opinion. I've also tried to rename the sticky topics and split them from the other topics to make them more easy to notice. Feel free to post more ideas to improve the mapping board and to help mappers to navigate - especially new mappers.