Regarding the scenic bit. Remember you are using live steam locos. You need a separate "steam up area". Preferably using wooden sleeper track, or a hardwood panel with 45 mm gauged grooves, butted onto a siding. LGB track has a habit of melting under live steamers left to brew up for too long (as do nice expensive Massoth rolling roads). Don't ask me how I know. Join
Narrow Gauge Railways in your Garden - Association of 16mm Narrow Gauge Modellers they have members in US and a number of groups operate indoor tracks. They even have a group wide "Modular" layout team.
My garden railway has an indoor section, photos below. Its a simple 2 line siding that joins by a hole in a wall (catflap) to go into my garden. All the vegitation you see on there was recycled from the scenery on the slot car layout I posted. Waste not want not. The base was painted mid green, and as the paint dried scatter material was applied. Track was laid and pinned on this. Then in went the ballast (potting grit) mixed with watered down PVA. Added "clumping" material to give it some texture, like weeds growing. Then liberal quantities of dyed litchen (varied to give it some interest. There are various bits of cork bark and bits to represent a rock face. Then I added trees, they come from various sources LGB, Buch, etc'. Off the shelf large scale are out there, some artisan made too. Most of this comes from regular model railroader suppliers. Then add buildings to suit, I used mostly shallow profile because of limited space - the sidings live behind my sofa as top of back cushion height ! You can Use Pola (LGB) and Piko kits, there are plenty of resin and laser cut wood specialists too. Then finally populate. Again lots of choice there, LGB, Preiser, Schleisch, Bachmann. But check your scale, most available are 1:22.5, your live steamer looks like a UK made 1:19.3 scale (16 mm). Oh, and one very important thing, I keep a small (about 12 " high) fire extinguisher handy.
Main thing have fun and let your creativity rip. Do it your way. I have seen some layouts that use 2 very disparate scales for fun effects. Like a miniature railways running by a full size one. Oh, by tge way I got so wrapped up in this I forgot to say wellcom. Max



