What was God's goal in creating life? I am agnostic and rationalist and I spend quite a lot of time reading the arguments of tenants of intelligent design (but rarely interacting with them). Regularly, one of these tenants claims something like "there should be a reason/cause for us to exist" or "life must be hard/meaningless without a purpose/goal".

I disagree with that statement, but it made me wonder: 

What was God's purpose, according to the Bible, to create life? 

I got that, once life is created, God, being a benevolent deity, wish for us to live a good life according to his Word, in order to go to Heaven and enjoy eternal happy life (in opposition to an eternity of torments in Hell). 

But, why creating life in the first place? In opposition to not creating anything or creating a universe with no life (a clockmaker is satisfied with the mechanisms he created, even though they don't bear life).

Boredom? Curiosity? Because he simply could? 

Is there anything about his intent in the creation in the Bible, or, is it claimed to be beyond our understanding?
It isn't entirely clear whether you're asking what is the purpose of all Creation or just of human life.  Either way, the fundamental answer is the same: for His glory.  

Isaiah 43:7 


  Everyone who is called by My name, whom I have created for My glory


Psalm 19:1 


  The heavens declare the glory of God; and the firmament shows His
  handiwork.


Romans 1:20 


  For since the creation of the world His invisible attributes are
  clearly seen, being understood by the things that are made, even His
  eternal power and Godhead...


Isaiah 45:18 


  For thus says the Lord, Who created the heavens, Who is God, Who
  formed the earth and made it, Who has established it, Who did not
  create it in vain, Who formed it to be inhabited...


Putting all of the above pieces together, all of Creation was made to bring glory to God, but more specifically, man was created to appreciate the glory of God, and the Earth to enable the creation of mankind.