In my Forgotten Realms campaign, I took a page from Douglas Adams and turned the gnomes into the overseers and custodians of the world, like the mice were for Earth. They are the tinkerers behind the scenes; adjusting the balances and powers to keep the Realms moving toward *their* vision of How Things Should Be. Just like the mice, the other races suspect nothing, thinking gnomes are funny at best, ridiculous and powerless at worst; which, of course, fits right into the gnomes master plan.
Only a hand full of individuals outside the Gnomish community know about this; in fact, less than 1% of gnomes know about it. The race of gnomes is organized like the Masons or Shriners in my campaign (helps to explain those red pointy hats as well ). The Gnomish Powers encourage their members to be tinkers, artisans, and illusionists, expecting this way that the cream of the cream will rise to the top and reveal themselves as being ready to be inducted into the deeper Mysteries.
When my players get high enough to start thinking of planes travelling, they will stumble across the Great Mission, and learn that the gnomes are the Spelljamming representatives of Faerun, sent here to look after the planet and shepherd the cultures toward being ready to join the universe at large.
