Hi Joe,
The canvas allows you to use a blank slate as your base - so that you can composite a project from scratch without requiring an image or model that comes from somewhere else that serves as most of the project's design. e.g. a project made of a bunch of individual smaller parts and some text rather than just one big image that covers the whole thing.
For instance, the signs my wife designed that we make for sale on Etsy are just an assembly of multiple parts she found and bought to use, different ornate pieces that she chose to use and where to use them. I took that idea and incorporated it into PixelCNC so that you could effectively do the exact same thing without using an external image editing program to do it.
You don't have to design projects in PixelCNC, and just load in a single image or a single model etc... but the option is there for users to streamline their workflow by eliminating the need for multiple tools ;)
- Charlie