Jixxxer -- I work with one guy who did quite a bit of rock work. He put the rocks/boulders along the shoreline. In one place, it was to stop erosion from waves. In other places, it was just because they looked good.
He also used some broken concrete slabs, as you indicated. I've never thought that they look very attractive out of the water, or even along the edge of the water (that's just opinion, I guess). Thus, he put those in a little deeper water for fish structure. You can see them from the shore when it is calm, but covered with algae, they look pretty good down there.
Dave
