I loaded a background image that I drew into Moho, but it looked a little flat. I wanted it to have something like line boil happening, but not to a distracting degree. So as well as the background image, I also imported an image of just the line art, with a transparent background, and used the Trace Image option to convert it to a vector.
By reducing the opacity of the vector outline, it works quite well as shading for the image underneath. Plus, I can add a little animated vector noise so that it has a little visual interest.
This is the original image

This is the outline that was converted to a vector

And this is the end result, the flickering might be a bit too subtle on YouTube though