Looking back and forth between the monitor and the ceiling, yes, that texture could work, especially below talus fields where run-out of individual rocks is exceeded by humus and loam growth, yielding sloped fields of widely spaced boulders, but…
I think the problem you will run into here will be the "wiping off’ the darker colors from the “rocks”. Touch any of my ceilings, and the “rocks” come right off, to make a mess all over the place. I think you’d end up having to handpaint this to pull it off, both the rocks and the interspersed lichen or grassy areas.
Something else. In areas like that I’ve seen, the rocks are half submerged in the soil, they’ve been there a long, long time. A few, the more recent ones, are on top of the earth, but by definition, you are below the frequent run-out zone. Then there’s color.
For rock glaciers and talus slopes, I use a variety of sized gravel, in several “coats”. I like to mix my “rock” and “dry dirt” colors and paint over the “grass” (green paint before vegetation is added) at the base of a steep slope, then sprinkle various sized rocks and sand over the top. Vaccuum up the excess after it dries, then use a nearly dry brush to splotch rock color over the talus, and repeat untl you get the thickness and texture you want. Then I partially add rock color, to match cliffs, partially add dirt color to allow for finer fills that drift down too, and leave some of the original color of the rock and sand to show through for variety.
Off topic a bit, but that’s what you’re going to want to accomplish, colorwise, in a boulder field too. The rocks have to generally match the cliffs, but differ enough to allow for variety. Most signs point to either hand-painting, or painting a tray full of rocks all at once, spotty, allowing other olors to show in some places, then placing them one at a time. I think you could get the half submerged effect by running a thin layer of lighweight spa