All of the pictures from this page were generated by Terragen, by Planetside Software. It is a program that generates landscapes using fractal algorithms and then renders them.
Terragen features a superb renderer; aside from the quality of the landscape, the scenes are lit with excellent volumetric lighting (which accurately uses atmospheric conditions and the landscape to produce shadows and haze) and water effects. Furthermore, rather than apply a texture map to the terrain the program uses far more satisfying shading routines. With a bit of work, it can produce scenes that are at least as good as scenes produced by far more expensive suites.
Some of my better efforts with the software are found below. Also included are some of the results of my brief experience with Bryce. The images are 1024 x 768 or above, and average around 250kb.
Terragen Links -
www.planetside.co.uk- The home of Terragen.
http://www.planetterragen.btinternet.co.uk/ - An excellent Terragen news, tutorials and resources site.
http://www.fractal-landscapes.co.uk/images.html - A gallery of very realistic images rendered in Terragen, but using fractal landscapes generated using the author's own program which seems to create some from impressive landscapes, although the author hasn't released it to the public yet.
http://www.terrasource.net- A comprehensive link-list of Terragen resources