Poser 7 doesn't really mind when it comes to polycount, it can render an awesome lot of polys without a hitch. It's the multiple hires textures that is causing the out of memory problems. Again, reducing texture sizes (those human figures probably don't need 4096x4096 textures, 2048x2048 is more than good enough) and replacing textures by procedurals will get you there.

In fact, I just finished a render containing this exact same temple prop, 15 human figures, 9 of which have strand-based hair, loads of reflections, IBL/AO, displacement,  hi-poly vegetation, the whole kaboodle.

The pen is mightier than the sword. But if you literally want to have some impact, use a typewriter

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