As always, your advice and input is extremely helpful, Youme!
In regards to the first shot: Thanks for the advice about the fence shadows. I didn't like them either, but I wasn't sure what I could do. As for the cliff texture, yep I agree it's a bit repetitious. I'm not a huge fan of the cliff as a whole simply because it's so plain. I'll mess with the scaling and rotation, but that cliff is one of the reasons that area is only 95% complete. I'd like to do something else with it to make it more interesting, I just haven't decided what.
In the third shot: I generally steer away from a very strongly colored light source like that, but in this case I wanted something to give the room some extra punch. The CP room is otherwise very evenly lit and doesn't have a lot going on. The room in which the light exists cannot be entered, but is there for visual interest. The light prop itself is from the spytech props and is a siren or warning light of some kind with the blue skin instead of the red. Close up it makes sense, but it's something I'm sure I'll be tweaking right up until release.
In the final shot: I thought the glass floor added something to an otherwise fairly architecturally bland room. I also enjoy being able to let players see each other without shooting each other. It actually makes for some interesting strategy. (ie. can I really put a sentry gun where it can be seen through those windows? Can I really use that space under the glass floor to uncloak or disguise as a spy?) In the TF2 universe I think the support structure around the floors is enough to explain away the fact that they may not be the most realistic idea. As for the supports themselves... yeah, probably too bland. I didn't want to use the same metal "I" beam texture I have been using in other areas, but I'll see if I can find something else to use.
Finally, you're right, I didn't bump up my settings this time around. Even though on my computer bumping up to decent screenshot settings gives me an average framerate of about 10, I'll make sure to crank things up for all my future shots. For beta and release shots I'll hand the map over to a friend of mine who has a beast of a machine that will display it in all its glory.
Thanks again for the comments! Since you seem to be the only one keeping tabs here I'll have to trust your advice implicitly.