Everyone has their own ideas and parameters of what a layout should be. Good reason why we like seeing others' layouts.
Mine has always been a degree of scale / natural scenery, but trees are all bottle-brush and pine cones that I paint, plus a bit of lichen and real rocks. I can get ballast out of our drive and rocks by the lake. I like to have a mountain / tunnel feature somewhere in a corner, using plaster over chicken-wire. Lately I have used spray foam / great stuff, spray it on, easy to carve when dry, can add thin layer of plaster over it.
99% of my accessories must be vintage Lionel, AF, Ives or German, same with signals. Figures are mostly lead, but a few plastic.
My Lake Shore Railway and Hole in the Wall Railway videos on you tube show how I combine these elements.