I just ran into this too. Seems the only work-around still is to copy the NPM package’s CSS to a folder in your project where it is loaded, then update the paths to the images in the CSS to your public folder where you can place the images.
EDIT:
Actually, it’s easier just to add the few lines in my app’s CSS file with !important that override the NPM packages CSS lines that load the images with the paths to the public folder. Then you can just import the NPM packages CSS as normal. This is a lot cleaner and requires less maintenance in the future.