Seems like I beat JamMeister again.
Hi sccergirl4u!
There are many softwares out there, sharewares, paid ones and freewares. Most people on this site make walls using 3D rendering softwares. Many of those use Bryce, some use 3DMax. Even AutoCad is used by some. And Rhino and Lightwave too. These softwares will cost you moolah.
I, on the other hand, use a freeware called POVRay available at http://www.povray.org and I think I don't do a bad job. Post rendering is done in Photoshop7 in my college (very costly).
Landscapes can be rendered in Terragen, World Builder and Vue d'Espirit.
People also use Paintshop Pro, Gimp, etc to make walls. The software you use does make a bit of a difference (paid software scores over freeware in ease of use, that's natural), but what ultimately matters, is your talent.
And talent is appreciated at this site!!!
I think this answers ur question bout walls.