The Artist's Toolset was something I designed to make my own life easier while building the game Mouth God, because I was tired of looking at a boring alpha-esc environment.
The whole system only took me an hour or two, and I use it in multiple projects and pass it around to many of my peers for rapid prototyping work before artists can really flesh out the environments.
The tool is a blueprint actor in Unreal Engine 4 where the artist or designer can quickly drop in a mesh, determine the area in which it will spawn, determine it's relative color and scale as well as whether or not it will have collision or if wind will effect it.
While obviously not suited to AAA development, it certainly makes life easier when you want to show off a nice looking prototype.
Oh and it works entirely with instances and material instances, so regardless of the number of instances you spawn it won't put the slightest damper on your framerate! The scenes to the left are pushing around 100k instances with framerates over 100.
On top of this, there are options built into the script to set it up in a more uniform and tileable way, which can then be used to quickly randomly generate city type environments, as shown below.