I know it's probably too late for a code, but I have a few ideas. First, an erupting volcano. You could be going up the base, the screen being shaken by earthquakes, and finally get to the top and plunge right in, stopping right before you hit the lava and then punching it all the way to the top as the volcano erupts behind you. Second, a winter night in a haunted forest. The snow would muffle all background noise, and you would hear creatures of the night breaking branches all around you. You'd start speeding up, periodically seeing a shadow of something, until you reached a clearing, only to have a haunted castle loom before you in a Castlevania fashion. You could use the castle as the next level.
@GrimAngelXx: One of the things we are working, is the support for packages/episodes. Since the number of cool themes to be included in the game is large and diversidied, it would be the best approach. For instance, we can package 3-4 levels in a haunted forest/castle package, or a wild west package, and so on. There are also the "fun" themes like @foxmulderino suggested (fast food, etc).
My AppStore review: 5/5, 16/2/2010 Fantastic! highly recommended! This game really surprised me as I wasn't expecting a lot but wow, I was wrong! This is a very good looking FPS/on the rails shooter, it runs very well and is very fun to play! Totally worth the asking price, buy it now!!! Hope that is ok