Wraith, each map can have a default (built-in) cloud file. And a different cloud file can be uploaded if desired, but there is no arena setting to toggle clouds on or off. It sounds like until HTC figures out the frame-rate hit, only a couple of maps have a couple of clouds on them. NDIsles is one of them, and there are clouds over the center island. They should still show up offline, you might need to give the map a few minutes to create the clouds. Just in case offline won't work, you can create a custom arena online and choose "ndisles" as the terrain. I just did and the clouds look really nice with the bump mapping turned on.
