Thanks all

Ties are simply Terragen cubes with displacement coming from old wood images and orange rag is a flattened Terragen sphere with several displacements including one coming from a cloth image.
Ballast stones and base sands are all fake stones (14 separate sizes) with procedural texturing only. Experimenting with a new crack modification scheme which makes some cracks fade, actually the reference doesn't show many cracks in the ballast stones nor much actual fine dirt.
Some of the stones may look squashed just because they are those random "cow splat" shapes that like to crop up in fake stones from time to time, reseed might lose them I guess, but I left them. There are funny "rocks" in real ballast around here, metal slag sometimes and pieces of fused glass like material or melted limestone from some industrial processes, industrial bi-products or waste seemingly.