no, at this time Jagex has not made it possible to switch races. At the moment you can only be a male or female human.
A Gnome Scarf is a possible reward from a Hard Delivery in the Gnome Restaurant activity. Other possible rewards for a Hard Delivery are Mint Cakes, Grand Seed Pods, Gnome Goggles, and many other items. You can also purchase a Gnome Scarf from the grand exchange.
Gnome
Gnome General Store.
Gnome.
in the gnome stronghold
purchase it at the Tree Gnome Stronghold from Rometti and his store, Fine Fashions.
Gnome.
You can find it somewhere near lumbridge or alkharid.
You can get to the Tree Gnome Stronghold quickly by using seed pods from the Gnome Restaurant Activity to instantly Teleport to the Grand Tree. They can be used once.
hes in the center of the maze
A gnome.
in runescape you can find swamp toads in the swamp northwest of the grand tree (Tree Gnome Strong Hold).