Did a quick demo drawing "cobblestones or flagstones" in response to a question for one of the classes at Sheridan last week...so here's the thing: make sure SOME of the EDGES of the stones go with the Grid, that is, the ground plane...this will help root the design and make "lie down" properly. Do not draw snakes or squiggly lines for a texture, they make the stone "stand up" and stones don't have such lines on them. (Ithink thereason peole draw them is they arean interpretation of the surface of the stone where it reaches an edge and drops a fraction; what they are drawing is the slight shadow cast by the edge. The quick cartoon stone texture is some short broken lines, don't know why but it works. Beware the cliche!
below: explaining why we draw the things the way we do: they come from a quarry, usually are of limestone or one of those stones made of strata, they then get worn down through erosion or hard use...they start off with sharp corners and end up rounded..or the corner breaks off, leaving a new angled edge.. These things look this way for a REASON! Better still, go outside and draw a few! learn the Truth! Beware the cliche!