I think the idea behind the map is very good, just a little lacking in the execution. With a bit more time this could be a very high quality work.
First off, it's just too small, you can volley from the spawn to the back on the net in ~0.6 seconds. Way too low, even for 2 / 3 per team.
The pbox areas are oddly shaped. While the distance from the edge parallel to the goal is fine, the sides seem much too close in. You can jump in on the side from the raised level, charge, release and you will be unstoppable.
Aside from that, just a couple of minor things. The texture on the curved walls should not be grass. Perhaps some kind of mud, dirt or rock? And even if you stick with grass there, make sure the textures align
-You also need to raise the walls in the area around the outer level. The ball shouldn't be able to leave the field if it gets shot up there.
-There are what look like curved lights around the ring. Either make them throw out light, or don't have them there. They just look out of place.
-Ambient sound wouldn't go amiss.
oh and everything DavidM said as well.
I really think this has a lot of potential, but if these flaws are not fixed, it will really kill what could be been a great map. Looking forward to the next release
