Over the years I've scratch-built all kinds of terrain, much of it to sell online - or to sit sadly in my gaming closet downstairs... Here's a few pics. Sorry for the inconsistent sizes, some of these date back three versions of this website.
Some rock ruins, made from pink styrofoam - always handy to distribute around!
One of my "ruin corners" - guide here
A trench terrain piece
Mounted on a bit of wood, hills and rocks made of bits of foam
Hills ade from styrofoam sheets, painted textured and flocked
Scratch built house (cardboard, balsa) and lumber pile
Miscellaneous terrain I sold as a pack - LOTR gate, the rest is scratch-built.
More ruin corners - these were built from foam-core.
Pink foam rock bits, mounted on random sized bases.
An example of one of my terrain boards - one foot square, I have quite a stack of these.
Outpost tower, scratch-built.
Branch from the back yard, plus some balsa and foam, mounted on a piece of MDF board.
Works well, but hard to store without breaking!
A set of rocks built as "scatter" terrain - made from chunks of styrofoam cut with a hot wire cutter and painted. You can see a bit of the styrofoam's texture showing in the second picture, but I thought it looked kind of cool. Mounted on an old CD/DVD disc - which was something I do quite a bit. 28mm fig for scale.
From one of my first auctions, so scratch-built rocks and a metal "dead tree", most based on sturdy wooden bases.