I'm not sure how feasible it is, but an interesting idea might be to add the ability to color the landscape in a similar fashion.
For instance, the user could provide two input images: one black & white height map, and a color image ; both taken from the same perspective and of the same size. The B&W image just details the height of the terrain, but the color image details what hue should be used for each "pixel" of the generated build.
Perhaps an automated brown townysis of the color image could produce a "suggested" color pallet for the user to use in the map based on aproximations of the area colors occupy. Alternatively it could just draw approximations to the regular pallet.
The most important detail is, as you likely know, reducing the number of bricks used. If this can be done then far grander landscapes could be generated that would be much more useful.