The contrast with the textures is really high, I would prefer it lower. Screenshot of the map with my settings:
I like the textures in the underground they look pretty neat. Regarding the crystals (or w/e you call it) in the underground, I think you should move them around a bit, would make for a more interesting look imo.
Regarding the gameplay, I don't like the 1st and 2nd flag positioning, it's pretty easy to defend both of them from the place above 2nd flag:
Ohterwise pretty nice map, low is slightly slower than normal way (low ~ 12 seconds from flag to flag, normal ~ 8 seconds) which is pretty nice, since it's easy to speed through and would make it hard to have fights there (reminds me of pp1 low kind of). Kind of hard to judge the environments, but from what I can see, it looks decent.