You can see some SS's about Plane Numbered 13
http://www.geocities.com/pencereoyun/13noeng.htm
I will use my own graphics for chapter 1 if I can't contact the artists.
Not a lot of "game play" shots but the ones you have are ok. There are some perspective issues that can be worked on. I also wouldnt use gradients. They usually only look good in 3D games and if you are going for the "stickmenish" style you have now, gradients wouldnt be your best option. Keep working at it.