One of the things I'm struggling a bit with as a 3D artist is knowing when to make things like piles of gravel out of real 3D geometry, and when to make it out of lumps that've been adequately textured. In the current set of images I'm working on, I knew that ultimately I was going to require both, so I first started out by making a Substance base.
I took the opportunity to actually put down six different color combinations of stones, even though I just needed one. Each stone is a different Substance Source texture, applied to modeled pebbles and baked out in Substance Painter, moved to Modo and simulated into a bed of gravel, rendered, and then moved back to Substance Designer for full compilation.
I'm seriously hoping this turns out to be a set of materials I can use a bunch over time, because rendering gravel takes a crazy amount of time! It did turn out a bit rougher than I'd hoped and it does have a seam (where the particle rocks rested against the collision box) but, since I don't intend to do any serious close-ups, it should do. The graph is SUPER simple but I put in a switch so I'd only ever need the one Substance to use it.
Renders in Substance Designer.