Here are my thoughts on the Ice Tower at Box Fort™
I absolutely love this design. The mayhem, the death,the freezing, the explosions!

Everyone and anyone may acquire an advantage in this kind of design, and I especially love the ice blocks and TNT ice blocks that can be used to completely rek hordes of attackers if given the opportunity.
It's a very big fighting space, I like it. It would be unwise to spam, as there are a lot of flanking opportunities, as well as chances to freeze or explode your enemies. Nobody ever stops moving, and it makes it even more exciting to tower in.
My only major issue is the flag, it usually always gets stuck in a corner and is very difficult to freeze due to the masses of players pking and trying to hit the flag. Like others have mentioned, it's probably a better idea to change the shape of the whole room, most have suggested circular. This way, the flag will never stop moving and players will need to create some sort of barricade to stop it, making it easier to hit the flag.
The idea of using a shovel to create snow that will act as a barricade could be cool, as it would open up more defensive opportunities. Of course the snow should melt down and should be easily destroyed by swords/bombs/lanterns, etc.
The idea of sliding around on the ice would give the tower another unique aspect. Sliding around while having to fight enemies could pose a challenge for everyone, and would require players to get used to it. The problem with this is that it would probably make it more difficult to hit the ice blocks into other players, or even the flag, but I digress. This could make everything even more rewarding, and I get a very rewarding experience utilizing the ice and TNT around me to take the tower. It's exactly what I want in a tower, and it's completely improvisational.
I've seen many skillful players use the ice and TNT blocks to dominate the playing field, and it's buying the whole team enough time to take the flag, or even buy enough time for the defenders to get back into the flag room after dying to defend the flag. I haven't had this much fun towering since I had a guild to tower at MoD with. This would be an exceptional tower for Snowtown, if that's ever a possibility.