In the jungle land known as the Tusk, the remnants of free human civilisation live alongside the Ongaro who outnumber and shelter them. The Ongaro are sentient apes who share a bond of kinship with their 'less smart' human cousins who represent the last bastion of their mysterious and largely forgotten heritage. The Tusk is a dangerous place filled with hazards and monsters, but it is certainly safer than the world outside: the battleground for the war that throttles the world between the Hawklite Sky-lords and their avowed enemies the Serpenteel Empire.

Beyond their border in the Mountains of Leng lies the inscrutable and impenetrable city-state of the Mentasians whose slaves are said to live in bliss. The Mentasians are seen as gods by those who have any knowledge of them, beings of unearthly and ancient quality whose history transcends the limits of history.

The Chakra-Cities of the Tiger Alliance are guarded by peerless warriors who serve a caste based system in the name of preventing the world from falling into corruption. Each city is located in a unique and specific part of the world and is ruled by Somaticians who espouse the use of Soma, the powerful elixir that gives the Tiger Warriors their power and the Somaticians their wisdom.

Seemingly beyond the world the city-state of Lunarsopolis lies seemingly beyond the edge of the world and the Sea of Stars. Here one can stand amid its exquisite and fragrant gardens and take in a view of the whole world. Travel to and from this fiercely independent state is done only with the support of its Merchant Princes and its lonely queen, Celestia Selene. Yet Lunarsopolis can be seen from almost anywhere in the world – if one's eyes are open at the right time. It is as near as it is far.

Gemsoulled are cursed with wanderlust; if they remain in one place they gather entropy in the form of Rust which will age them and eventually decay and destroy them. For this reason they are perpetually active/moving. These machine beings are born of ancient alchemy unknown even to them. There are rumoured to be dangerous places, in the world, known as Genesis Pits, wherein the Gemsoulled were once (maybe still) forged. Such places are toxic and dangerous. The Gemsoulled come from an age of machines and are not the only living remnants of that time. It is supposed they were fashioned as soldiers. But other machine creatures exist; some guard the Genesis Pits they occupy: Dieselasaurs and Steam Dragons rumoured to be the size of villages consuming and corrupting all with their mechanical toxins. One Genesis Pit is known to be near the Tusk and is a source of many lost treasures (or so the stories go). This is also the home of the Lord Weird Shiva – the Wrought God. He is a being that has made the Pit his home and used it and his knowledge of forbidden sciences, to become immortal. His followers (slaves) are known for riding tamed Dieselasuars on raids throughout the area; may Rivas are the subject of his personal experiments using the power of the Genesis Pit on mortal flesh.

***

I don't know how to exploit these ideas, but they are born of a far future-esque (ie implied) sword & sorcery (& planet?) setting.

Step 1:

Who are the PCs and what do they do? Not just your actual PCs, but PCs in general. If I come in saying "I want to be an awesome ninja dude with a sword" you say, "OK, you're probably from.... where they ....".

well, the pc's are adventurers int he traditional sense: the wander around the world getting involves in adventures with people, places and the conflicts therein. Fairly standard stuff. I just don't know how to flesh out the setting ideas!

How do these adventurers support themselves?  Is there really enough "free loot" hanging about to support them?   And where did it come from?  And why haven't others gotten it before now?

How do the nice people around them feel about these guys, who are bascially the equivalent of a biker gang or mercenary company?

Those aside...

This is a nice fuffy start.  There are a lot of pretty ideas here.  Now, making them manifest.  Take one place and focus on it.  You can go hard core (http://www.strolen.com/content.php?node=1148 ) or just begin to write ideas about it. Or a story.  That way you can get a handle on it.   You can take an inbetween track: choose one area. Ask yourself what would you need as a player character in that area. What would you get from the GM?  Okay. The second part of that is, what do I, as a GM, need to run the setting?  

After doing any one of these methods, go on to the next area.  You have kind of listed six there.  Start with that.