The most awesome thing I've learned from Genesis 1 came from studying it with my Strong's Concordance at hand.
The Hebrew word that is translated as "man" in v26 is 'zakar.' The literal translation includes "the remembering one." So what is man to remember? He is to remember God - His character, authority, and precepts.
God created man to have dominion over the Earth with the intention that we remember Him and emulate Him. Genesis also tells us that we are created in God's image. Looking ahead to Chapter 2, God tells Adam to name all the creatures. Together, this tells me we are to emulate God by speaking His order into the darkness of this world.