This material for Dungeondraft has a chunky bark exterior and a rough textured wood pattern. I went through several variants on the way: a wood grain texture didn't look right since the map is top-down and tree rings didn't play nicely as a seamless pattern. In the end I decided on a simple rough diagonal grain - drawing inspiration from the marks a blade leaves on rough-sawn lumber.

Example use cases would be if you have very large trees or very small player characters and need to depict tree trunk cross sections or branches.