Free GM Resource: Grey Tower Games YouTube Channel
Grey Tower Games is a "newer" channel that has, at the time of this post, fewer than 400 subscribers. That isn't a lot, especially when compared to the other channels I've posted as resources.
What I really liked about GTG is that these builds generally tackle terrain building from a completely different perspective. Instead of heavy use of cheap foam core and lots of hot glue gun action, there is a lot of sculpy and modeling clay. I like being able to add a few new ideas to the table, and I think those of us who make terrain for their games will like Grey Tower Games as well.