Scott,
Good comments here but may I add a slightly different approach. Being a large man (like me /DesktopModules/NTForums/themes/mls/emoticons/crying.gif) and not being physically agile, you may want to re-consider building anything you have to get up on a walk across to retrieve derailed trains, fix a stubborn turnout, or to service the scenery. I would advise against it. The beauty of your new building allows you to design a layout that permits you to access your entire layout while standing on the floor.
To do that, the layout benchwork should be more shelf-like with wider areas only where you need return loops (at either end of a very long, bent dogbone). You can even build a double dogbone with inner and outer loops for two-train operations, yet maintain no wider than 4 foot platforms along most of the run. You could bump out an area in the middle for some additional trackage, scenery or whatever, but wherever it is wider than 4 feet, you will need an access hatch to come up from underneath to reach the back. The back corner of then "L" would naturally be deeper to allow 8 foot or larger radius curves, but other than the ends, that would be the exception.
Consider the modular layouts that we all see at the large scale trains shows. They are all built on narrow sections but scenicked to the max. What I am advocating is a bit deeper than those modular units but I am sure you get the idea.
This does not limit your design possibilities at all. Consider many highly detailed raised platform G scale pikes that have been featured in GR and other mags - many of them they have long, straight narrow sections where the viewer can ge up close and see everything. Also consider that most prototype railroads do not have many sections of their right-of-way other than freight yards that are more than a few tracks wide. You can use grades and elevation to provide visual seperation of rear tracks from tracks next to the front edge of the benchwork. And no one says you have to keep all tracks ruler-straight on the long sections either. A bit of lazy curving back and forth can add visual interest especially if in a rural setting.
I encourage you to consider a plan where both you the operator and viewers alike can step up and see the trains closely and not have the trains 7 feet away at the back of a deep platform where they can lose the "wow" effect because they are visually smaller. It will also make your gradual progress much easier as you can stand on the floor or sit on a high stool to work on a section and still reach the back. /DesktopModules/NTForums/themes/mls/emoticons/tongue2.gif
Oh, and to freply to, your original question, I agree with the flat black ceiling - make it visually disappear, but I prefer soft incandescent floods that can be dimmed down for those twilight or night running. That means you will spend some time lighting your buildings, trackside areas, city streets, etc. You will definitely want to be able to reduce ambient light for night ops. Also, my favorite lighting is indirect - where lighting is both behind the mountains for twilight/sundown effects, and also overhead but behind baffles to conceal the point sources.
Food for thought.
Al