Most of my terrain are made to be used in Mordheim, a skirmish game using 28mm figures.
Mordheim is about a bunch of heroes (and followers) running around in a ruined city or somewhere else where there are a lot of interesting terrain to explore and sometimes dive into cover behind.
So we need terrain. A lot of it. As long as you can store your terrain, you can't get too much of it.
In the basic setting, Mordheim, mostly ruined gothic buildings and some walls, wells and that kind of stuff.
In Lustria the terrain are more Inca-like: steppyramids and lots of wilderness (rocks and trees).
You can buy a lot of terrain, and some of it are actually good, but why waste money on something that you can make cheaper yourself (OK, sometimes rather more expensive, but then that's because you have gotten yourself into a new hobby: building terrain)
Basing cardboardbuildings
Primitive huts
stonelook
Ruins from mosgummi
Sacrificepole
very simple
Jungle
2 versions
Small stone structures