As the saying goes, "the more terrain, the better the game".  Part of the fun of miniature war gaming is making your own terrain. The only limit to what you can build is your imagination (and maybe your wallet). Here you can find a sample of some of the terrain that I have built over the years. For inspiration I visited terrain sites all over the net, the best (in my humble opinion) is Terragenesis which is maintained by Gary James. If you can't find it there, you don't need it.