Also used in advertising are symbols.
In this Last Best West poster, the wheat sheaves symbolize prosperity. Wheat was the main crop grown in the prairies, and the golden wheat stacked in piles suggested that riches were easy to come by, with a little farming work.
The baby that the young woman is holding is also a symbol. The baby, healthy and happy, is meant to portray the Canadian West as an excellent place to raise a family. If you settled there, you would be happy and have a large, healthy family, according to the poster.