My plan all along (after ripping out most of my original around-the-room benchwork) was to build individual modules so that the room could easily be repurposed as needed.  We've hosted several exchange students for 2-3 weeks at a time and this room is where someone would stay.  In preparation for just such an event, I decided to dismantle my under-construction freelanced Olympia & Southern Railroad, based on the actual TacomaRail Olympia branch.  We didn't end up hosting so I didn't complete the demolition, leaving one U-shaped 3'x5' section in the former closet. 

The new plan meant constructing the modules and then connecting them temporarily with bolts, which sounded like a good plan.  Below is a pic of the first two modules, each 16"x48".

They were just basic construction with a 1" layer of foam on top.  I bolted them together and then painted them in a sage color similar to one recommended by Lance Mindheim. 

I had the shelf at the bottom so that I could put all of my storage items underneath. 

Then added some black cloth skirting that was from my original layout some years back (but never completed - that's my usual m.o.).

My plan was to also construct the closet area modules but ended up not having enough wood.  I hadn't yet ripped out the old layout section here so I decided to retain it and just attach these modules to it.  It was a few inches wider and not completely perpendicular to the wall at the connection point, so butting the modules up to it left them at a slight angle to the wall they were against.  Not enough to be a problem but not perfect. 

This view looks towards the closet area and the existing benchwork, which I completed with a taller fascia to account for the difference in height and the thickness of the old roadbed, which included 2" foam. 

The industry in the foreground was originally going to be Hancor Plasctics (aka Advanced Drainage Systems, Inc) in Belmore, WA on my last layout.  I had Elvin at Layout Concepts custom make the silo combo to match it, but never got to finish the layout.  I've decided to use the same industry but place it in Phoenix on my new line.  This is just getting a feel for things.  The hoppers are on the spur feeding the facility while the freight cars to the right are on the SLTR's "main", with us looking north. 

The blue foam is the start of the old benchwork.  To the far left will be the interchange yard with the Union Pacific.  Beginning at the blue foam I'll need to drop in elevation by about 1 1/4", which I'm bummed about because the area is so flat, but will live with anyhow.  I could have chosen to build up the old benchwork with additional foam but I didn't want almost 4" of foam and the requisite deep fascia to go with it. 

Aside from the elevation difference between benchwork, I made two other compromises with the layout plan that I **hope** will not be too operationally limiting or frustrating.  One was that I decided to orientate the interchange yard parallel to the rest of the layout, which meant that there was less than 4' of space to have a train swing onto the UP main, clear the switch to the yard, then back in.  This would require that the yard be fairly short (and stub ended), and would require a lead sticking out into the room either permanently or as a swing-up/down type of affair.

Ultimately I decided to make it the extension for the yard lead/UP main permanent, extending about 26" out into the middle of the room, parallel to the main benchwork as well as the door entry.  While not ideal, at one time I had filled this roughly 10'x10' bedroom with an around the walls layout including a center peninsula, with just 18" aisles.  I share this room with my wife's crafts/gift items as well as some of my daughters stuff (and turtle) so it was an inconvenience to say the least.  This extension won't be perfect but it shouldn't interfere much with their use of the space. 

In the picture above, a train has pulled onto the UP main heading west off of the SLTR "main", and is preparing to back into the interchange yard, which will be to rear left of the train.  As you can see, the wall isn't very far away so the yard tracks will be quite short. 

Because I don't want it to look like a stub end yard, I plan to put a mirror of some sort at the end against the wall, giving the impression that the line continues on into the distance.  As I lay track and start mocking things up a bit, I'm getting a feel as to how this will work.

The picture above shows a head-on view from the end of the extension.  You can see where I've positioned an old mirror against the wall to make it look like the trains go off into the distance.  When finished, I think it will be effective enough for me in at least eliminating the dead-end look.  I'll probably choose a smaller mirror and try to block the right half with a building or something in order to make it less conspicuous. 

In the photo above, you can see mostly just mocked-up items.  The train is swinging onto the UP (ex-SP) main in Tolleson.  It will pull clear of the west yard switch, then back into the unfinished yard to set out its train.  It will then pick up the UP interchange and reverse back onto it's own line and head south.  To the right is the planned Maricopa Beverage siding, based on the Columbia Beverage siding in Tumwater, WA.  It basically consists of a single track with room for a tanker to pull alongside and pump out what it needs.  The building will actually be for a trucking company that shares the space. 

Well, that gives more of an overview.  I'll probably try to post some more ideas soon.

-Dave