Improved and Expanded!
I’m gradually getting the hang of Redbubble. Which basically boils down to giving them a .png they can’t mess up.
This is harder than it should be.
I seem to get the best reproduction by taking a photograph, boosting the contrast, then washing it through Inkscape to create a vector, then resizing it to create a .png which includes a reasonable border. Otherwise, the algorithms at Redbubble have a hard time centering the art. The worst part so far is dealing with the greeting card - they do not provide a product-level image-placement editing option in that category, so one is left placing the art on a wall poster and hoping for the best. ::shrug::
Anyhow, enjoy my fledgling efforts. They wind up looking kinda like this: