Great concept! As a time-starved hobby game dev, the focus on being able to make something quickly from a reference image is really refreshing, in comparison with the more common design approach geared toward those with deep, well-practiced polygonal modeling skills.
I like the direction your interface is going in. I love the Skin Modifier in Blender, but the workflow for that does feel a bit tedious, so I like the click-to-add-node approach. I also appreciate being able to move the rendered view around the window and scale it as desired.