An early concept image from Destiny, back when it was a pure fantasy game.
Pillars of Destiny's World
Hopeful and inviting
Idealized reality
Filled with mystery and adventure
Where you can become a legend
Joe Staten and Christopher Barrett refer to each Halo game as similar to an Alaskan pipeline: a narrow slice through a large world, where art and other assets are used one time only, in linear sequence, with no reason to return.
Destiny, by contrast, will promote exploration, multiple visits, and change over time.
Bungie's latest Community Focus features the Guardians of Destiny, makers of the excellent Guardian Radio podcast. Bungie also points out that the latest Guardian Radio episode features JPL scientist and Bungie fan Craig Hardgrove, whose work is also going to feature in a future episode of Anger, Sadness and Envy, coming up (hopefully) soon...
Following Bungie's presentation at GDC by Joe Staten and Christopher Barrett, which you can read about at Bungie.net or watch over at GameSpot I've updated the Destiny concept art gallery and added the short Destiny Character Development video shown as part of the presentation.