Also say it "looks good"
As much as a lot of people don't like the look of a pile of rocks, one thing it does provide is cover and sleeping places for your fish. A pile of rock doesn't have to look bad.
I think you might want to provide some cover.
Vary the heights of the structures and avoid symmetry. When your corals fill in, the details in your structures will be eclipsed so think of basic structures in proportion to each other. I like the last pic best, lots of negative space.