12 foot ceilings are quite common is garages especially if you plan to install a floor hoist. You could always install roof trusses on 4' centres to fill up some of the unused space. It is a useful looking box Carl
I've built a couple winter dioramas and have used Styrofoam boards for the snow banks. The blue extruded stuff for flat areas and the white bead board for banks and lumpy areas. I used drywall compound and Woodland Scenics flex-paste to smooth things out. The white beadboard should work well for the roadside banks in your dio. Carl
I use plastic knitting needles for shafts and rods, They machine well and work with styrene glues. In Canada they are sized in millimeters I'm not sure how they are sized in the States. 5/16th = 7.91 mm therefore an 8mm needle would be the equivalent size. Carl
When we built our house several years ago I claimed a room at one end of the basement as my model room. This is where I build, store and display my models. I started out by building a 12 x 8 foot display table like a model train board.
This worked well for my truck models but didn't work for my dioramas. It is now filled to overflowing so the models expanded into other parts of the basement. The first display case i bought was a 100 gal aquarium.
This works well but is very heavy. I have it on an industrial stand with wheels under it. There is an extension on the lid to accommodate the over height hydro pole. Everything has to be added from the top down which is a pain when working on the lower tier. Many years ago a local jewellery store closed and I bought one of their display cases. It is a single level 5’unit. I have a couple dioramas in it
I later bought a couple more jewellery store cases. Since my wife passed away a little over a year ago I have migrated these cases for my models to the main floor of the house. They are both mounted on casters and easy to roll about. Occasionally I take some of them to construction shows in the area.
These two cases are the ones that have some of my more treasured models and dioramas. Some of the rest of my dios are hanging on shelves in the model room
Or appear on this photo diorama which is a backdrop for many of my work in progress models that you may have seen in the past
Out in my garage are a pair of freebie cabinets that I use to keep many of my diecasts and a few models