One suggestion on the lighting.  If you are generating the jail cell etc in C5, put in a small barred window in the back of the cell, have  a shaft of diffuse sunlight come in through it at an angle.  This would give the cell some more depth and detail and give you a very nice lighting effect.  Check out my latest gallery entry for an example of this kind of effect. http://excalibur.renderosity.com/mod/gallery/index.php?image_id=1253773

I tried to keep the lighting levels somewhat low but keep a bit of detail in the render.  Also if you are using C5 for the cell, try adding a bit of displacement mapping to make the bridks or concrete blocks stand out and have some texture.

 

Just a few suggestions.