Lets imagine for a moment, that there was a civilisation, a civilisation of insects, and there were two or more societies within this civilisation. And then, let us suppose that these societies found that they did not agree on everything, and perhaps sought different solutions for the betterment of their world. Let us further suppose, that one society thought to better their world by creating microscopic self-replicating harvesters, and another sought to better their world by creating insect/stone-elemental/missile hybrids that could last forever and were conditioned to cooperate and obey orders, but were quite entirely too insane to understand the concept of orders. And perhaps, just possibly, other groups also found ways to better their world...
So, lets us imagine that the harvesters converted all matter to a depth of half a kilometre and then exhausted all available energy reserves, and then, over time, were(mostly) reduced to sand. And lets also imagine that the hybrids found that they were not entirely comfortable with those events and left, and now the planet has some lovely rings around it, bit of which may get curious from time to time and pay a visit, and maybe even the entirety of the rings might get curious if ever anything REALLY interesting happened.
So endless sand, with water (and the occasional viable but inert(for now) grey goo) in the lower reaches. There would be resources under the sand, but the deeper you go the more likely you are to encounter some sort of extremely hostile secret military-style science-gone-mad project sealed in some sort of difficult-to-process or deeper-then-the-goo-reached container. And occasionally a monster falls from the sky, unless you fail to control your emissions, in which case the sky falls and it is made of monsters...
Or perhaps the worlds could be combined?