here's another point to consider:
by saying that we try to capture the purest nature in our aquascapes, untouched by man etc, are we thinking that we HUMANS are not part of nature itself? Think about it for a second...if aliens (if they exist) were to look at the Earth eco-system, how would they view human? IMHO they'd see us as they would see other animals - Fauna, omnivourous mammals, homosapeins; as we are part of natural system.
of course i admit that we human beings are a bit greedy, building large structures, clearing large areas for development etc.
in aquascaping context, how would you define mixing plants native to the Amazon and South East Asia for example? Is it "capturing nature" at its purest? Natural look perhaps but far from pure nature IMO.
That said, I wouldn't mind looking at figurines & toys or even man-made structures in the scape, as long as it fits the theme. I'm not a fan tho but if its done right, it'll be one nice to look at
