Here's what I had for a Christmas 4x6. I had a platform 4" under the main surface that held the tree stand - so only the trunk came through the board, and it cleared the trains underneath. Used 42" curve on one end and mixture on the other, with Marx O-27 manual turnouts for the siding. My nephew's 4yr old son LOVED it. I had multiple buttons to push and lights and sounds.
Under the "snow" is a 1/4" black foam pad that I got cheap at Habitat Restore. Same rubber you see used for the roads.
Sky blue poster boards for a light and simple backdrop.
Wintery wrapping paper cut into stream shape, and slot car railing used for bridge over the 'frozen river'.
Oh - and black painted 1/2 popsicle sticks for RR ties. Just sitting under the track.
