When I start a project I tend to dive in headfirst on terrain as I work on the miniatures. As a natural packrat, I had several things stashed away that would suit the Turnip28 project perfectly (and double for Rangers of Shadow Deep).
One of the elements are strange root funnels. These were dead easy to make, as I had bought some decorative driftwood that was already a weird pale blue. I glued these to some hardboard bases and used a latex window caulk called Alex Plus to make more organic roots and tendrils. Make sure to get the 'paintable' caulk.
A few dead trees using my standard methods.
My most recent terrain items were made about two weeks ago. I needed some dangerous terrain, and while my plan was to mark dangerous areas with critters, I also wanted to have some dedicated patches. While pools of water and mud seem to be common, I opted to make some nice dry ground... which of course someone seeded with bear traps.
This pig sty is from Infinite Dimensions as well, and can double as a defensible terrain, or a dangerous terrain if I place some boars in it.
Some gabions I had on hand, not quite sure why I originally bought them.
Lastly, a table surface. Its a rather bad piece of particle board I had, covered with a textured, gritty deck paint. I painted it, added some flocking here and there, and painted in some polyurethane in a few spots to create a glossy wet and muddy look. The final coat was a heavy spray seal of Plasti-Dip clear.