I played on this server for about half an hour, it was fun and all, but I think you could make some improvements.
First of all, the time before the lava comes is way to short, if I were you I'd set it to 1 minute to let new players search for potential survival spots. Maybe two minutes on the first round, it's all up to you.
Talking about survival spots, right now there's always the one best spot where everyone goes to. I fin thatd the only way to fix this would be to create completely new maps. They don't have to be very detailed at all, it could just be a bunch of colored cubes thrown together.
I'm pretty sure the gamemode is not intended for it but I would love for co-operative play to be encouraged. You could for example have a very high spot, where if a player gets to it (pushed up) there's a button to let everybody else up.
But wait! If he gets up there, why would he press the button and not just wait for everybody to brutally drown in lava? Well, you see, they could just send another blockhead to "get rid" of this bastard.
Talking about events and whatnot, why not create a bunch of fun buttons and events? You could create a button somewhere along the bottom of the map that punishes the people on the top by firing missiles torwards them or making their floor dissapear, your could have a bot dispenser on one side of a big gap and a button on the other, if someone pushes the bot to the other side and has it land on the button, a bridge appears for a couple of seconds. The possibilities are endless and it's kind of sad when every game has some asshat get to the top first and kill anyone and everyone that walks trough the cramped hallway leading to the top.
Now, pretty much all of this can be done by other people once the game mode is released and I might actually create a map myself - but hey, add this to the release version and you might get more people interested.