my two favorite cube scapes are a singular center island or the bonsai look. the single center island should somewhat immitate a large seamount, possibly even breaking the surface, IMO this gives a very natural look as it is common for seamounts to hold vastly diverse amounts of sea life. for the bonsai look it would also stem from a single island per say, but instead of being in the center, start it from a corner and build it up and out with dramatic overhangs, something about the shadows large overhangs create that make corals stand out just that much more. just my $.02!