Help with flow of map plz :D

Let me start off by saying hello im new to the community and unrealed so dont be to harsh on my for future refernce lol... Anyways back to the topic I am trying to make a chemical/sewage/icky stuff treatment plant (whichever i decide to make it ) map or something along those lines and usaully at any kind of plant or warehouse they have some type of office where managers or people will go to sit rest and get paper work done etc. What kind of things would I incorporate into the level to make it look like it goes from the treatment center to like an office room or something alog those lines while maintaining a sort of industrial look but keeping the idea of this being an office within a plant. What textures could I use/BSP Editing and Static meshes to make this map look reaistic.... Here is some pics to show you what kind of environment the main plant is....

Sewege/Chemicals or w/e this is at the bottom

This is the bottom level where all the crap is...


This is the middle level hallways which will lead to the offices and whatnot...


This is the top level of the map where old hardware crates and other things will be its pretty much a storage area of the map...


So know that how you see the texturing and lighting and whatnot in the map could anyone help me make the transition from plant to office?

I guess what im trying to get at is what would make the environment realistic looking like if you were to walk from a real plant that treats sewage or w/e into the offices of that plant, what kind of things would you see on your way there, because an industrial setting to an office setting is obviously going to require a change in scenrey so i want to know what would make it look like, "this is what offices in a treatment facility would look, and this is what the hallways would look like to..." here is a link to the map as you can see it is extreme alpha and its only my second map X.x so there is no botpath or anything yet because I like to finish all the environment stuff first.

http://excabus.envy.nu/we2.ut2

thanks for your help shank ill see what i can do now

thanks for the links superape ill be sure to take them into consideration ive already read 1 of those :>