While my products generally won't have a specific setting other than "Pathfinder" or "Old School" like many DM's I am an inveterate world builder.
Over the years I developed 5 fantasy worlds for my gaming and no they don't really reference the Five Stones in the company names. Thats actually a coincidence.
Now each of these worlds served a different gaming goal at one time or another
The first of these Midrea was a built around the idea "What are the logical consequences of a D&D world being real" -- it was strange and in its final 3x version (it had been 2e, GURPS and a homebrew at one point) it turned out to be a magical cold war with a lot of Sword and Sorcery and Cthulhu elements.
The Second, Enarion (also known as Along the Great River) was means to trim out most of the Tolkien and Faerie Tale bits and leave me with something more inspired by Lieber, Howard, The Bronze Age and Pirates of Dark Water.
The Third was Eradim and yes this is a the reverse spelling of Midrea. It was Midrea after most of the magic was gone and the technology advanced to about 1650 or so. This allowed me to keep my setting intact but change the play parameters a bit, something I found to be a time saver. Its fare more romantic fantasy meets gritty history meets swashbuckling than its parent.
The Fourth was Mekethkier. The premise there was "Evil Wins" It predates Midnight (I created for the WotC design a setting contest) and was much less bleak. Beyond that I only remember a little about it .Since a goblin ate my notes, I can't tell you much more.
The fifth and my most recent is "Faerielands" which is basically D&D with all the Sword and Sorcery edited out and a heap of faerie tale and smidgen of horror. For me it serves the same goal as the Mandragora setting
does for Scott. It provides me an easy tool set for gaming faerie tales and limits the pallet to appropriate flavorful material.
Of them, only the last might see print. There is in my opinion a real need for an action faerie tale RPG using a familiar system. This kind of set up is great for younger players and as a starting game at least in my not so humble opinion.
The other worlds like the thousands of homebrews out there will remain unpublished and only enjoyed on the web and by my players.