I agree: the second screenshot is excessively dark. Balancing darkness is tricky, of course. When you get to the detailing stage you can make an "excuse" for it being somewhat dark...broken lights, etc...but for now put some lower-power point-lights to give it something.
I think the comment about the central point is good: there needs to be a bit more cover or visual breakup. You could probably use a few extra rocks or something to achieve this without much trouble.
Ultimately the "cover" issue is best fixed by playing the map on a gameday/impromptu, so I'd encourage you to submit it for one. See how it plays, and where the spots that are overly exposed are, and then make adjustments.
Edit: I forgot to add one thing. Even though this is an alpha, don't be afraid to use a bit more variation on red/blu sides. The central building is good, being neutral, but maybe use some of the red/blu dev textures for the respective bases to give players more visual cues about their location.
Keep at it!
-Colin