Looks very nice.
Some more stuff to do, I'll try not to post stuff that other people already mentioned.
I'd add some settings for the sun lighting to the worldspawn. Maybe something like this:
"_sun_light" "250"
"_sun_angle" "72 -25"
"_sun_ambient" "30"
"_sun_diffuse" "60"
Add "angle" "#" to the player spawns, that they don't look in front of a wall or a box after spawning.
Oh, and maybe add some ammo packs
Some more screenshots...
Red: Some of the arches are looking crooked.
Red: Here're small edges you need to fix.
Red: Here, too.
Red: One misaligned face.
Red: Move the ladder out of the wall.
Red: Add clip brushes here.
Red: I'd like to see clip brushes here, too.
Red: Move the tree a little bit or rotate it with "angle" "#".
Red: Hm...you can shoot the nodraw brush in the air. That's very weird. Maybe split the nodraw brush that you have one wide brush on the ground, one middle wide brush in the mid and one small brush on top to fix this.
Online @ [OTB] Beta!