I'd like to an an image (ideally an SVG) as an inset to an existing graph in R and put a black border around the image.
Is that possible with base-functions in R? Do I need packages for that?
Maybe the grImport package is what you are looking for ? It only seems to allow to import Posctscript files, however.
You can find two vignettes files on the package web page, which should help you learn how to use it.