It looks like the bigger the screen, the bigger the image generated :) so maybe there is a good way to trick it into generating print-quality images
By messing with my screen settings I was able to get cards of about 749 x 1260 pixels (per card - the png images I got were bigger). That is *almost* the image size required by a POD tarot card service.
I will add svg export: these are vector images, so it shouldn't be too hard.
Here is a trick (for Chrome): set the zoom level to 25%, click the "Enter fullscreen" button, then choose "Save image as..." in the context menu. The resulting image will 4 times larger than your on-screen image.