Kubera is ruler of the demons and ghosts.
Later in time he became the ruler of earth ghosts who are the guardians of the earth treasures.

With Indra,Varuna en Yama they are the Digpalas, the guardians of the 4 points of the compass.

Kubera is often depicted with a big belly, symbol of wealth.

Attributes:

Mongoose (Nakula) :
A Mongoose vomiting jewels is associated with god of wealth Kubera.
The mongoose symbolizes wealth and abundance
The mongoose is guardian of the snakes, who are the guardians of the earth treasures.

Water carafe (Kamandalu) :
Water symbolizes life, fertility and wealth.
With the carafe it is possible to collect amrita, the nectar of life.
When needed the amrita can be pour out again

Bag of money:

Pomegranate: