I've got no personal experience with bryce itself but i've used other 3D software.
What looks to have happened is that no anti-aliasing has occured giving it the pixelised look, so you probably have to turn that on somewhere.
Also it might have to do with the wierd resolution you've selected, why 810x607... in the past i've had problems when selecting non-standard resolutions although not to this extent. I'd be able to tell you more if I knew how to use bryce
Edit:
http://www.daz3d.com/support/faq/index.php?id=212...0bf634dc910a59b4ee
Try reading that... its the only thing i could find on the Bryce website
http://bryce.daz3d.com/Bryce5_Manual_DAZ.pdf
Also in the manual page 314-316 that seems to be all the quality options for renders.. with anti-aliasing on with an image like that it will probably take ages