Genesis 1:26 expresses the specific purpose statement of the Bible. God, the Creator, the Master Potter, is reproducing Himself! This is THE work of God. He is in the process of making man in His image. That project is completed in two stages, the physical and the spiritual. When the physical aspect was completed at creation, the spiritual one began. This is the overall project He is supervising.
God is already a unit: "Hear, O Israel: The Lord our God, the Lord is one!" (Deuteronomy 6:4). God is one, but consists of more than one Person. When Jesus came, He proclaimed the gospel of the Kingdom of God. In doing this, He publicly announced the expansion of this unit to include others besides the two Beings already revealed.
A kingdom is synonymous with a nation. It consists of large numbers of people, but it, too, is one. Indeed, the church is called "a holy nation" in I Peter 2:9, and though it has many members worldwide, it is one church. Thus, Jesus announced that the Kingdom of God will consist of many more personalities. He also told us how we can become a part of it and how it will be accomplished. Through these means the project stated in Genesis 1:26 will take a giant step toward fulfillment.