This is what I did last year. It's both STD and O. The whole thing was made out of xps foam. After Christmas, I stored it up in the garage rafters so I'll be trying to reuse it this year. The central tree platform is made out of wood. If you have the ceiling height, then a tree platform is an easy way to squeeze in another loop.
I'll change it up this year but I'm not sure how yet. I realize it's a little over-the-top but maybe you can get some ideas from it.
Couldn't find a bowing smiley indicating the "we are not worthy", so the thumbs up will have to do! (Wayne's World for anyone not knowing the reference )
That is pretty darn cool! And I envy your ceiling height! (maybe not so much for heating though... )
I've never done anything that involved, but normally do an oval loop of O84 FasTrack on the outermost loop, then a tubular oval loop made up of O72 (though I think I eased it in recent years with either O81 or O96 for the 2 pieces closest to the straight edge of the oval on each of the 4 transition points). Sometimes I may space it such that I can run one of those loops through a Hellgate Bridge.
Then I often add one or 2 small O31 loops on either side of the tree to run handcars or small motorized units (snow plows (which may actually pull a car or 2), speeders, etc).
I don't do anything fancy for scenery, but do have some of the O Gauge accessories that I will at least put out as a static decoration if I may not wire them up (Santa Pylon, Santa/Nutcracker/Gingerbread gateman, etc). Maybe a couple Dept 56 or Lemax buildings.
I'll try to post some pics of previous years. One time years ago when I was still in my apartment I incorporated the (new at the time) Lionel Swing Bridge in front of the tree. Just static (never could have operated it in the space available), but had an odd shaped almost rounded triangle loop of track around the tree. It was at floor level (for at least one or 2 pieces of track ) in the back and then rose using the stock risers to get to bridge height in the front.
-Dave