I've been working on a Mirkwood terrain board for a few months, on and off. Frequently, artists depict Mirkwood as a tangled, overgrown forest full of gnarled trees and tangled roots. Here's a still from The Desolation of Smaug. To my eye, there's nothing interesting about this kind of forest - it's become the 'go-to' forest design for any fantasy setting (Snow White and the Huntsman, e.g.).
Tolkien's own drawing of Mirkwood is quite different, however. Endless rows of fairly uniform trees create a kind of eerie semi-monotony. What is more, old-growth forests often have little in the way of undergrowth because the trees are tall and the canopy dense enough to block out most of the sunlight, and few branches survive on the lower portions of the trunk. So this is a more life-like representation of an old forest.
Here is Siegfried in a forest in Fritz Lang's Die Nibelungen.
And here's a still from Orson Welles' Chimes at Midnight, when Falstaff and his pals waylay some travelers and are in turn set upon by Harry and Poins.
I find these images much more interesting and affecting.
Here's what I've got so far. The trees are just dowels of different diameters, wrapped in toilet paper soaked in watered-down glue, with roots made of twisted floral wire bound in masking tape. By varying the colors, textures (from sawdust), and the direction of the TP wrapping, one can create a number of different tree types. The leaf litter is from JTT, and the mushrooms are from a Polish company called Ristul (I think?). I intend to make enough to cover the whole table, but these were the trial run.
Not the best pictures, and the effect is ruined by the bright sunlight in the background, but that's the idea. Will try to prepare a more scenic backdrop next time.