Nice loco!
If you want, you can mount strips of tar roof paper as "draping" of the boards, since(at least in Sweden) its covered with fine stone gravel. So it gives a very plausable road bed look. If you want, you can add even more gravel. For outdoor use, the proven method is to mix the gravel with the kind of very fine "concrete" like stuff you use for housing tles in kitchens and bathrooms.
A good source of just the right size roadbed material, is bags of different sizes an colors of decorative gravel used for fishtanks. Visit you Zoo shop, and be sure to look at the catalogue of what the can order for you! The selection is quite surprisingly varied!
A maybee not so proven method, is just to use generous amounts of regular paint as a base "glue" underneath surface. I use a variation to this method, when making coal stacks and coal loads for wagons and locomotives. I first shape some styrofoam, and then use a lot of matte clear varnish to glue the stuff together. The matte varnish is completely undetectable once it dries. For styrofoam, the varnish has to be water based - else the styrofoam will "melt".
This is actually what I'm planning for myself, since all track so far has been mounted on boards. (Long story.)
Adding a few plants, fences, bridges, a tunnel of sorts, telegraph poles, signals and a station building, as movement references, makes the running look much more varying and dynamic.
For a while I worked as a film & TV producer. The firts thing I learned, was to introduce as many static reference objects as possible, to make the movement in the picture as dynamic as possible. And we are all programmed to give attention to movement, as opposed to static visuals. (I would guess, probably for survival purposes, since moving animals and people, generally are more important than trees and stuff.) Especially at the far end of your track, the train will look much more slow, nearing "static", unless there are closely placed reference points. (Catenary has this nice effect. But wooden telegraph poles are more romantic - and cheaper to make!)
A bit surprising, I've found that lighting actually adds a lot, even in daylight!😄 If you can add lights to your locomotive and coatches, do so! The actual relatively few number of hours we run our trains, makes it very feasable to just use a battery or two in every coach.
I haven't tried lighting inside buildings yet, but I suspect that would also look nice. (I know it did in my childhood's HO scale days.)
Rule number one with any layot build, is to get something running as soon as possible. Because that energizes the continuation of the layout build! I can not stress this enough.
