Change audio file preview image (not icon) in Finder?

I know this is easily done in iTunes, by simply changing the "artwork" of the song.

But I need to do it outside of iTunes, and I need to change the preview image and not the icon image.

Many tutorials show how to easily change the icon for a file, but I've found nothing about changing the preview...

As said I need to do it within Finder, or maybe with Quicktime? I don't know what method I can use, if any.

I need to have the artwork I want already in the file before importing it into iTunes, doesn't matter why I won't get into that.