We considered basic flat paneled trim but ultimately decided it was too craftsman for our colonial home. Instead we went with this:
It is thicker than the wainscoting so the transition from trim to wainscoting would make sense.
First I had to remove the old trim, then score seam to separate the trim from the jamb, held together by a dozen layers of paint and caulk. This ensured I didn't damage the drywall or the jamb, neither of which I was interested in replacing. Finally, starting at the bottom, I slowly pulled the trim out of the wall with a pry bar.
Ready for new trim!
Next up, wainscoting!