I've moved into a new house and am in the process of setting up my "mancave" and getting everything else in there.
The way the "mancave" room is designed, it has a high slopped ceiling that goes from about 8 feet at the lowest point to 11 at the highest. There is a little 1 foot wide ledge at the back wall about 9 feet up. On that ledge, I've placed most of my 1:6 items, save for some boxed pieces and the large tanks. On a wall space below the ledge and above the doors, I have 1:18 planes hanging on the wall. (I've never done that before and am pleased with the results).
I added some Ikea "Billy" shelves at one side of the room to hold books and models. I keep my 1:18 armor in the deeper cabinets with the glazed doors. Books, 1:32 planes, 1:32 tanks and other assorted items fill the smaller shelves. A few 1:18 planes have been placed on top.
There are more 1:18 planes on the ceiling and some on a display table under the window.
I've got various other 1:18 and smaller scale items scattered in other rooms, but the biggest concentration is in the mancave.
This is still very much a work-in-progress. Eventually, I'll have pictures and posters on the walls and likely a different assortment of aircraft than what is seen. Still, I'm really enjoying the chance to make my own display room, but one doesn't realize how much they have accumulated over time until they have to move it!