About the theme: the actual theme don't fit. Such layout with random borders could fit better in natural themes. I think that the bottom of a jungle with glowing fungus could be appropriate.
The map is too big with walls too small. Small walls help soldier to kill/farm infected, scientist can move too easily and witch can spawn infected through them making the game completely random. You can solve both problems (size of map and size of walls) by making everything bigger and remove some rooms. It will be easier to move inside and less prone to abuse/exploit.
The top of the map should be not flat but diagonal or like a mountain. It will be more interesting to play.
In general, try to imagine each class in your map, and how the infected will progress.