I see what you're saying Mad, but there are no set rules.
In this level, I actually like the symmetry, it was used well. One little thing is where the lights of the water went up onto your table... it's nothing big, but the blue on the brown is just too obvious. Move it up a few places
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On a side note, I hope you don't do those lights on the water all over Rudora, as nice as it is I hope it's not overused.