This years Christmas display

[lugworm]

Just a very small (13 inches across) OO gauge layout to keep my grandson and younger relatives entertained. Needs more snow, a few people, a foot crossing, and maybe some more lighting.
Because the circle is so tight, I can only use an 0-4-0 tank engine with probably one open wagon.
I'll put more pics on when it's lit up and running.

[fourtytwo]

Fantastic, what a good idea, maybe give them the bug in later life

[bulleidboy]

Very good - you could almost use it as a Christmas cake decoration

[Mountain Goat]

I like that. For adding wagons or coaches you may find the couplings are the limitation. Using a different design of coupling instead will enable trouble free running.

I make my own for 7mm narrow gauge use which are a bit too large for 4mm scale, but the principle behind them can be put to use as an option if required.

Alternatively, keep the large tension lock loops and have an L shaped hook which is extended so it is more reliable.
Removing one tension lock hook and running with the single hook does work but is a little suseptable to uncoupling at a small bump in the track, which is why an L shaped fixed hook that one lifts the wagon in place maybe a reliable option to use.

Just a note on my design. I have curves that turn through 180 degrees on a 2ft wide board. They should work even narrower then this but the limitations will be bufferbeam overhang on longer vehicles and the flatness of the buffer will need curving in to help with the angles. The drop loops need to be kept wide if curving to the extremes.

There are other couplings that will work. Amazingly Kadees can work on curves down to 18" diameter as I have seen them in use myself. Admittedly the locos and vehicles were short with limited bufferbeam overhang.
You may find the false buffers that 00 gauge has may need to be removed or shortened if they get in the way. Shortened will retain the look without them getting in the way.
(I call 00 gauge buffers false buffers as the real buffers are the tension lock loops).

13" diameter is very tight, but it is not impossible to add rolling stock with some thought, which is why I suggest ideas to redesign couplings to cater for this.
I would try to retain the tension lock loops if possible as the stock can also be used when running with other 00 gauge items on larger layouts.
I really love your little layout. It is nice.