There's a new feature: you can now create multiple parts with a single CAD file. They all must be able to be cut from the same stock material. This should save setup costs and the hassle of having to connect parts together.
I used this recently to create a multi part gearbox (shown in the image for this post) for a fighting robot. I'll be adding a description of that, with photos, sometime in the near future.
You can't create multiple parts with a single raster (PNG/GIF) file just yet.
Updates for this feature to the online documentation are forthcoming.