I thought the sand idea was good but unless the gravity in this environment is much stronger, the flow and falling of the sand is way too fast. Also, the falling sand from both sides has too much volume and looks really angled/sharp on the corners. Push it back a lot.

The detail, as you already know, is pretty lacking. Right when you pass under the whatever you want to call it to go to a base, every texture right there is the same. You could also add some white spotlights (not literal spotlight ents though) to make the lighting more interesting.

One other thing, I find the part right outside the flag stands to be pretty dark, light it up a bit?

I want to note that the sand falling behind the glass was a nice idea too.

I would like to help you a bit with this map, I can add some more detail, lights, maybe optimize the geometry a bit to make it more playable and fix those stairs of yours! I could do a bit more complex texture work as well. If you'd like this contact me and I'll show you my version of your map ^_^

This is a map packed full of nice ideas! You maybye should consider slowing down the sand, as someone already mentioned.
You also should think about expanding the layout to the sides imo, i will get bored at this in 5 minutes.
I dont like the fact that you have to jump into the bases, you should lower that step, that will make the gameflow better!

may I modify the map too?
This way I can learn from you and compare to what dairyking does as well

I'll get to learn faster that way