I've known there are bugs in the SVGs pretty often, because they're not
very well attended-to—I noticed pretty quick that the Marble Eyrie, for
example, has its Body asset saved correctly in PNG, but its SVG is just
another copy of the head, oops!
I think SVG is still a nice default for this UI, but I added a little
form to switch to PNG, to give us a debugging method and escape hatch
if it starts to get weird.
