Attached Link: http://artzone.daz3d.com/wiki/doku.php/pub/tutorials/bryce/bryce-terrain09

Are you familiar with the terrain editor at all?

You enter it by clicking that "E" in that little sub-menu that shows up when you have a terrain or symmetrical lattice selected.
Here is a tutorial that explains the process of using an image as a terrain (or symmetrical lattice) better than I can do.

If you have trouble understanding the process, get back to us here.  Someone else may have a good tutorial.