I was away teaching over the weekend so no postings/pics... apologies. Am now finishing up the left side of my wall piece... another wall of adobe bricks and small stones. I am double stitch outlining stones here. FOR THE SMALL PLACED STONES ( REALLY OVERSIZED PEBBLES) ... I DON'T PLAN TO QUILT THEIR SURFACE AT ALL. Not doing so will add a variety of texture on the wall, and since they are quite small... it won't contribute to surface distortion.
For the larger adobe bricks, I continue texture filling with my irregular round plus sharp direction changing maze pattern I label this the "indecisive worm" fill. I came up with this fill years back when quilting painted asphalt. It seems to work here too.