I really need to get on the ball and make more levels, only managed one this week (blame Mass Effect). I did go back and make some touch ups to the first level by changing the outside walls and ceiling. I also created the foreground image that will fix some of the perspective issue when the player gets to close to the walls.
I have also been messing with different screen transition ideas. One was that between our levels the camera would quickly pan up and settle on the next stage to give the illusion that you are really assenting up. Random assortment of pipes would act as a bridge between the structures.