Level 10 is the first snow level of the game. The weather progression was one of the first things we all agreed upon. Around that time, Ripper's coding tutorial, that incorporated snow and rain, was relatively new, and as such we wanted it to be featured heavily. The progression in the game is as follows: sunny, cloudy, rain, snow, rain and then it's all cleared up again. The changes in weather also helped spice up the environments somewhat. I personally feel that there is a distinct change in atmosphere when comparing the 'normal' levels to the snow levels. Coupled with AlumiuN's shading that influenced the parallax sky, you get something that creates a distinctive atmosphere for a level. Something which shows in level 10.
Level 10, named VIP Executions after the boss area where executions take place, was one of the first levels where I fully used the 64x64 grid of the map. It's a big level in itself, but next to that it is also a boss level. Unfortunately, the boss is the weakest spot of the map for me, because it suffers from the same problem that most bosses with rockets suffer from in this mod: they blow themselves up. As such, the boss isn't challenging at all, and a major disappointment really.