you still working on this map or is it abandoned?
as for theme id go for an abandoned, overgrown modern ff map. make it a bit darker give it a somber feeling if you will. like with cracked healing pads (that still work), damaged flag room some roots growing through the cement. the roofs mostly collapsed. debris litering the area make it seem like a once great map that has seen better days. stuff like that. just a thought its might just be me though.
ps make it raining