Gnomes have a rich language of gestures as well as a "hand language" for use in noisy environments. Some of this is shared with the dwarves, while some is specific to gnomes. Gnomes use it both to conspire against the dwarves or keep conversations private, and also to express emotions that they can't or don't dare to express verbally.
Gnome gestures mentioned so far:
Putting a hand horizontally across the lower half of the face and glaring over it: a joking rude gesture, such as one would use to a friend.
Waving a hand past the ear on the same side: "What can you do?" Like a shrug.
Wriggling the fingers: dismissal of concern.
(Not strictly a gesture): a sibilant sound indicating skeptical dismissal.
Backtilt of the head to acknowledge and greet someone.
Human culture also has several gestures, including:
High Golds clasp one another's elbows in greeting.
Other humans press palms together.
The military salute is an open hand over the heart.
Putting a hand to one's forehead is the equivalent of raising a hand in class.
Bumping the sides of one's fists together (palm side upwards) indicates self-congratulation.
When sitting, the relative vertical position of one's head and one's conversational partner's head indicates claims of status: higher, equal or lower.
In the Islands, touching the thumb rapidly twice to the other fingers indicates "grab and hold on", a mark of approval, particularly of a potential mate.
Among the beastheads, pointing with the hand is rude and considered aggressive; one points with the eyes or by a gesture of the head.
Eye contact is considered important among beastheads, and a sign of trustworthiness.