Huhm so simple design but good for the start.I recommend to use a wall segment to close the dead way.Try to put some stone or grass or maybe tree.It will look like outdoor scene.I recommend yo to download Cosmic Prophet Model.Some of it have a tree model,grass and many more for a good start.I think this game can be great if you always try and try to improve your design.
Go here for cosmic stuff dont say thanks to me,just say thanks to Cosmic Prophet for his model
http://www.fps-files.com/download.php?list.23
Poloflece,Anayar,PWP,Henry Ham,Cosmic Prophet,Wolf,KeithC,Nickydude And Lee Bamber is my icon.