After reading about SamyPlaysSMBX's Wood Thwomp, the idea of this popped up in my mind. It's been niggling at me since, so I took five minutes to stop and make this. It's basically a Thwomp with the SMB3 wood texture, which is basically how I envisioned this thing. Right click and save it as npc-37, the mask is the same as the default one. Credit would be nice, though I don't really feel it is needed. Thanks to SamyPlaysSMBX for the concept.
It's kind of given me an idea for a theme of enemies with different block textures, so you may see other Timber enemies pop up at some point.