Found this image on a google search.

Wondering if there is any way to create this kind of thing with brushes or any other PS tool from scratch. Basically repeating trees trunks of varying looks and sizes for variety and depth (more specifically Apsen, if it matters).

Image is here: http://terryfarless.com/crImages/c2428_011.jpg

You can make the "trunks" with a basic round brush, add some grunge with brushes using different settings and the little notches in them and with lighting you can make them.
They wont look *real* but with work I suppose you could pull it off.

Another idea is to use textures, specifically that of an Apsen. o_o