Ideas, either in the form of paintings, writings, cartoon strips or inventions, comes from reading and experiencing. From doing stuff. Experiencing new things.
By going through life on a routine, doing the same thing day in and day out, ideas can be drain out. Routine, a human behaviour, dulls out life.
Reading is a good source of ideas. Reading is cheap and mobile. Reading is experiencing other people experience. Reading is harvesting ideas. As long as you read without prejudice.