Nothing at all.
I had originally planned to have gnomes as a homely, agrcultural people with a knack for tinkering, rather like hobbits crossed with the sterotypical back-room boffin, probably all smoking pipes too. As the campaign has developed, the tinkerer/artificer aspect has become the hallmark of the dwarves (well, the race of dwarves that most people meet) and of one major human nation, and that left the gnomes as basically homebodies. Since no-one has played a gnome in the 5-6 years of my world, or ever expressed any interest in them, I'm retconning them out of the world.